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Acceleration   Acceleration is what occurs when the car moves forward from a stop or from a slower speed to a higher speed.
Accelerator Pedal   A foot operated device which, directly or indirectly, controls the flow of fuel and/or air to the engine, controlling engine rpm. Also called the gas pedal. See Throttle.
Accelerator pump   Accelerator pumps are found in cars equipped with carburetors. When you accelerate, the accelerator pump delivers extra fuel through the accelerator pump circuit to allow the engine to deliver more power.
Accessory   Refers to a power-operated feature on a car. For instance, power windows and power locks would be considered accessories.
Accumulator   A container in the air conditioning system used to remove moisture or water. This helps to extend a/c compressor and other component life.
Actuator   An electrical mechanism for moving or controlling something indirectly instead of by hand, such as a door lock. Output device the PCM controls such as solenoids, relays, fuel injectors and stepper motors.
Air Conditioning   An Original Equipment or Aftermarket accessory system that cools and dries the incoming passenger compartment air. Aka: a/c
Air filter   This device filters the air that goes into your engine. Without an air filter, harmful particles would enter your car's engine and cause internal wear and damage.
Air pump   Many emissions systems include an air pump, which pumps fresh air into a vehicle's exhaust to help complete the combustion process and reduce emissions.
Airbag   A safety device, consisting of impact sensors, computer, a detonation device and air bag, that protects the driver (and in some cases, the passenger) in a crash by inflating a cushion hidden in the steering wheel and dashboard.
Alignment   Alignment is when all your wheels are pointing in exactly the right direction. If one wheel is off by even one or two degrees, it is considered out of alignment. When a vehicle is out of alignment, excessive tire, steering system and suspension system wear may be the end result.
All-wheel drive (AWD)   An all-wheel drive system has differentials which split the engine's power to the four wheels according to which have the most traction.
Alternator   An alternator is an engine-belt driven device that converts mechanical energy into electrical energy. The electrical output keeps your battery charged and operates your vehicle's electrical system.
Anti-lock braking system (ABS)   ABS uses a series of sensors, a computer and a high-pressure hydraulic pump to prevent your brakes from locking up during sudden stops on slippery surfaces.
Anti-roll bar   The anti-roll bar is a suspension system component that helps a vehicle to stay flat and not lean excessively when cornering. Also called a sway bar or stabilizer bar.
Anti-theft code (radio)   Many modern radios have special anti-theft circuitry that prevents them from operating after being disconnected from a power source. For these types of radios, it is necessary to enter a factory-supplied code to get the radio to work again.
Antifreeze   The fluid mixed with water that is put into your vehicle's radiator. Antifreeze is traditionally green in color; however, newer long-life antifreezes may be red or orange. Please refer to your vehicle's owner's manual for the proper antifreeze for your vehicle.
Automatic choke   Automatic chokes use either a heat- or computer-controlled element to turn on and off automatically as needed.
Automatic temperature control   A computerized system that automatically maintains a selected temperature for your car's interior. Also called climate control.
Automatic transmission   Automatic transmissions have hydraulically operated gear sets, which require no gear shifting or clutching by the driver.
Axial   Referring to a type of air conditioning compressor that compresses the R-12 refrigerant in a horizontal cylinder and piston compressor. Compare to Radial. (Remember, Axial is LONG like an axle; Radial is SHORT like a radial tire.)
Axle   The shaft around which the wheels rotate.

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Balance Tube   A tube or pipe connecting the exhaust head pipes in a dual exhaust system. This balance tube acts like a pressure equalizer enabling both exhaust pipes to flow at the same pressure.
Balancing (tire)   The process of making sure a tire will not cause vibration when driving. By using a computerized machine, a technician can locate a non-balanced tire and balance it by attaching weights on the wheel rim to even out the tire's balance.
Ball joint   A joint between two parts that allows movement in any direction by the two parts. Ball joints are most often found in a vehicle's suspension and steering systems.
Barrel (carburetor)   A barrel is a venturi in a carburetor where air and fuel are mixed, then taken into the intake manifold and then to a cylinder. Carburetors usually have from one to four barrels, depending on the engine application.
Battery   An electrical storage container designed to produce DC voltage by means of an electrochemical reaction. This reaction occurs in the container between the lead plates and sulfuric acid. Voltage is supplied to the starting, ignition and other electrical systems.
Bearings   Bearings are used to prevent wear when two moving parts are placed very close to each other.
Bleeding   Bleeding removes fluid from a system, such as a brake or clutch system. When a technician bleeds a brake system, the old fluid is completely removed and replaced with new fluid.
Blower Motor   An electric motor with a fan designed to supply a current of air at a moderate pressure. A blower usually consists of a fan assembly, a motor, and a suitable case. The blower case is usually designed as part of the heating/air conditioning system.
Blueprinting   The procedure of dismantling an engine, measuring, machining components, and reassembling it to the minimum factory tolerances. This procedure usually will provide more power and efficiency
Body   The assemblage of components, including windows, doors, seats, etc., that provide enclosures for passengers and/or cargo in a motor vehicle.
Body Control Module (BCM)   A device powered by the main vehicle computer that takes input from various sensors to control components such as the air bag, headlight sentinel and door chime.
Brake   A device, such as the disc or drum brake, for retarding motion. This is usually created by means of friction caused by a clamping force from a stationary caliper or shoe, against a rotating rotor or drum.
Brake booster   A device that uses engine vacuum or hydraulic pressure to multiply or boost the pedal effort of the driver while braking, thus adding more hydraulic pressure to the brakes for added stopping power.
Brake caliper   A c-shaped device used with disc brakes. When a driver presses on the brake pedal, the caliper piston squeezes the brake pads against the rotor and causes the car to slow down or stop.
Brake drums   Brake drums are drum-shaped components which contain internal brake shoes, which expand and press against the drum, when the driver presses on the brake pedal, slowing or stopping the car.
Brake fluid   A special type of hydraulic fluid designed specifically for brakes. Brake fluid transfers the motion of a driver stepping on a brake pedal directly to operate a brake caliper or wheel cylinder.
Brake lines   Metal tubing and rubber hoses which connects each brake caliper or wheel cylinder to the brake master cylinder.
Brake master cylinder   As the main component of a braking system, the brake master cylinder takes the pressure applied to the brake pedal by the driver and distributes it evenly to all four brakes on a car.
Brake pads   Brake pads are used specifically with disc brake systems. The pads fit inside the calipers, and create friction and stopping power when pressed against the brake rotor. When you have your disc brakes replaced, it is often just the pads that are being replaced.
Brake pedal   The pedal to the left of the accelerator pedal that controls a car's brakes. When you step on the brake pedal, the car slows down or stops.
Brake rotors (discs)   Brake rotors, or discs, are fitted to most modern cars. They are flat, circular plates that rotate with the wheel when you drive. When you step on the brake, the brake calipers squeeze the brake discs, slowing or stopping the car.
Brake shoes   Brake shoes are used specifically with drum brake systems. Brake shoes fit inside the brake drum, and are pressed against the drum by a wheel cylinder when the brakes are applied, thus slowing or stopping the car.
Braking system   The braking system in a modern car consists of the brake pedal, a power brake booster, brake master cylinder, brake lines, brake fluid, brake rotors (including calipers and pads), and, for some vehicles, brake drums (including wheel cylinders and brake shoes). In addition, all vehicles have a parking/emergency brake. Taken together, these components operate in sync to slow or stop your car. They operate like this: when you press on the brake pedal, the pressure you apply is multiplied by the brake booster. It is then distributed by the brake master cylinder and sent via the brake fluid through the brake lines to each individual wheel. When it arrives at a wheel, this pressure causes, for instance, the caliper (in a vehicle with disc brakes) to close, which then causes the pads to come in contact with the brake rotor. The resulting friction causes the car to slow down and eventually stop. Should this system fail, then the emergency brake may be used as a backup to stop your vehicle.
Burning oil (engine)   Oil burning occurs when one or more internal engine components fail, thus allowing oil into the engine's combustion chamber. There, the oil is burned along with the air/fuel mixture.
Bushing   A piece of rubber or plastic that fits in between two components. Bushing protects the two components from excess wear and damage.
Bypass   Providing a secondary path to relieve pressure in the primary passage. One example would be a water pump or thermostat housing bypass in the cooling system.

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Caliper   The housing on disc brakes which holds the disc pads and straddles the brake rotor. When hydraulically actuated, the pads press against the rotor, or disc, to stop or slow the vehicleÆs wheels.
Camber   It's the adjustment of a wheelÆs alignment where the top of the wheel is moved inward or outward from vertical as viewed from the front of the vehicle. Incorrect camber reduces tire life.
Camshaft   A camshaft, with phased cam lobes mounted on it, regulates the opening and closing of the intake and exhaust valves. Driven by the crankshaft via a timing chain or timing belt, a camshaft has a big influence on engine power characteristics.
Canister   An evaporative emission canister contains activated charcoal which absorbs fuel vapors and holds them until the vapors can be purged into the engine when it is started. It is a component of the emissions control system.
Capacitor   An electrical device for accumulating and holding a charge of electricity. A capacitor is usually found in an electronic ignition system.
Carb   See Carburetor.
Carbon Dioxide   A heavy, colorless gas that results as a product of complete combustion. It is considered a greenhouse gas.
Carbon Monoxide   A colorless, odorless gas that can be found as a product of incomplete combustion. Breathing high concentrations can be dangerous.
Carburetor   A mechanism which mixes fuel with air in the proper proportions to provide a desired power output from a spark-ignition internal combustion engine. On production vehicles, carburetors have been replaced by electronic fuel injection.
Carburetor jet   A fitting inside a carburetor that meters fuel into a metering circuit where it is mixed with air in the venturi.
Caster   An alignment spec where an imaginary line through the ball joints (steering axis) intersects a vertical line through the front wheel center. Positive caster delivers directional stability and improved steering feel.
Catalyst   A substance that can increase or decrease the rate of a chemical reaction between substances without being physically consumed in the process. A catalyst, which reduces engine emissions, is used in a catalytic converter.
Catalytic converter   An in-line, exhaust system device, containing a catalyst, which reduces engine exhaust emissions. Converters are located near the exhaust manifolds or headers for maximum efficiency.
Charging system   The system which maintains the electrical charge in your vehicle's battery. The charging system consists of the alternator, voltage regulator and battery.
Chassis   The suspension, steering, and braking components of a vehicle. Everything but the body, fenders, etc.
Choke   A device in a carburetor which shuts off airflow so that the engine runs rich. This is necessary to start a cold engine.
Circuit   A complete electrical path, usually includes the electrical energy source. May also be used with fluids or air. The headlights and brake system are examples of an electrical and hydraulic circuit.
Cleaner (Air)   A housing holding a filter fitted in the intake system of parts requiring clean air. An engine air cleaner filter removes particulates before they can enter the intake system and cause damage.
Clear-coat finish   Many modern cars have a clear-coat finish. This is an extra, clear layer of paint that goes on top of the last color coat of paint to protect it from scratches, chips and other environmental damage.
Climate Control   Describes temperature/ventilation environment in the passenger compartment. Climate adjustments are made by adjusting the heater/ ventilation and A/C controls. Aka automatic temperature control.
Closed Loop (Engine)   An operating mode of the PCM enabling modification of pre-programmed instructions based on a feedback system. By constant exhaust sampling, a closed loop system allows pre-programmed engine adjustments to occur while running in order to minimize exhaust emissions.
Clutch   A mechanical device which uses mechanical, magnetic, or friction type connections to facilitate engaging or disengaging two rotating members. Examples: the friction clutch located between the engine and manual transmission or the a/c clutch.
Clutch - cable-operated   A cable-operated clutch uses a metal cable between the clutch pedal and clutch fork to control clutch engagement.
Clutch - hydraulic   A hydraulic clutch uses a hydraulic circuit between the clutch pedal and clutch fork to control clutch engagement.
Clutch disc   The friction material lined plate that delivers power from the engine to the transmission.
Clutch pedal   The pedal on manual transmission cars that operates the clutch.
Clutch throw-out bearing   A bearing that lets the clutch pressure plate and disc smoothly engage and disengage with minimum wear.
Clutch-operated fan   An engine cooling fan that uses a heat-activated, viscous-fluid clutch which turns the fan on and off as needed.
Code   A system of symbols (as letters, numbers, or words) used to represent the meaning of information. An engine trouble code shows where a vehicle system or component failure may be occurring.
Coil (Ignition)   A device consisting of fine wire windings around an iron core, which is designed to step up battery voltage. The high voltage created (35,000 volts or more) is delivered to the spark plug so ignition can occur.
Coil Spring   A spiral-wound steel wire coil, of various wire diameter thicknesses and coil stack heights, used to suspend a vehicle. Can be used in cars and trucks, both front and rear, depending on the application.
Combustion   The process by which the air/fuel mixture burns within an engine to create power.
Combustion chamber   The area in the cylinder head where air/fuel is ignited to create power.
Comprehensive insurance coverage   Comprehensive coverage includes protection against theft and accident damage, regardless of fault.
Compression gauge   A special gauge used by technicians to measure how much pressure a cylinder can create.
Compression test   A test to see how much pressure a cylinder can create.
Computer (PCM)   Many modern cars have a central computer called an engine control unit (ECU) or powertrain control module (PCM). This controls the car's fuel and ignition systems by taking information from various sensors to determine how to run the engine with the most efficiency and power.
Constant Velocity Joint   A coupling that allows a shaft to turn continuously at various angles when coupled with another shaft. Usually associated with front-wheel or all-wheel drive vehicles.
Converter (Torque)   A fluid coupling device which multiplies torque between an engine and automatic transmission/transaxle. When a vehicle is stopped, a converter allows enough fluid slippage, so the engine can idle without stalling.
Coolant   A fluid used in the radiator for heat transfer. Mixed with water, coolants usually contain rust inhibiting additives and provide antifreeze protection. Some new vehicle coolants are designed to last 100,000 miles. Please refer to your owner's manual for the proper antifreeze for your vehicle.
Coolant reservoir   Many cars have a clear plastic reservoir that allows the owner to see the level of their vehicle's coolant. Check your owner's manual to find the coolant reservoir on your vehicle.
Cooler   A heat exchanger that reduces the temperature of the cooling medium. Two examples would be a engine radiator or oil cooler.
Cooling system   The system of components that keeps your engine at the correct operating temperature. The cooling system includes the radiator, radiator cap, coolant reservoir, cooling fan, water pump, thermostat, hoses, heater core, heater valve, and antifreeze.
Core (Price/Charge)   A payment that is credited back to the buyer after they have returned a rebuildable ôCoreö unit to the retailer. A rebuilt alternator purchase would have a core charge and would require returning the old one to receive the credit.
Cracked paint   Cracked paint occurs when a paint is so damaged, the surface actually develops cracks. These cracks may spread in a spiderweb fashion across the surface of the paint. Cracked paint is unrestorable, and must often be completely removed when a car is repainted.
Crankshaft   The engine component which converts piston reciprocating (up and down) motion into rotary motion at the flywheel or flexplate. Connected to the clutch or torque converter, engine torque is delivered to the drivetrain to move the vehicle.
Crazed paint   Crazed paint occurs when paint is so damaged, the surface actually develops hairline cracks. These cracks may spread in a spiderweb fashion across the surface of the paint. Crazed paint is unrestorable, and sometimes has to be completely removed when a car is repainted.
Cruising   Cruising is a driving style whereby the driver maintains a set speed with very little fluctuation.
CV joints   CV (constant velocity) joints are part of a car's driveline. They allow a wheel to rotate freely in any direction while still receiving power from the axle.
Cylinder   Cylinders are the large round holes in the engine block in which combustion occurs. This combustion forces the piston down and turns the crankshaft.
Cylinder Head   A removable part located on the top of the cylinder block; it usually contains valvetrain components and combustion chambers. For an overhead cam engine, it contains the camshafts as well. A head is an important influence in determining an engineÆs overall power and efficiency.

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Data   General term for information, usually represented by numbers, letters and symbols. A gas gauge is an instrument that provides data to the driver.
Defroster   A setting of your car's heating controls that lets you easily remove frost and fog from your vehicle's windows.
Diagnostics   The process of identifying the cause or nature of a condition or situation. Most cars have computer diagnostic systems that help the technician to determine corrective repairs.
Diesel engine   A type of engine that uses heat caused by engine compression rather than spark plugs to ignite its fuel mixture. Diesels are often more economical than gasoline engines, however they create extra noise and vibration.
Dieseling   The continued running of a spark-ignited engine after the ignition is turned off. There are two basic causes of dieseling: surface ignition, where combustion chamber surfaces remain hot enough to ignite fuel after the spark is terminated; compression ignition, where the conditions of temperature, pressure, fuel composition and engine idle speed allow ignition to continue.
Differential   A component of the drivetrain with an arrangement of gears designed to permit the division of power between two shafts. A differential also lets two wheels on the same axle rotate at different speeds. With out one, cars wouldn't be able to take sharp turns. Differentials are located in a drive axle housing.
Distributor   Part of the ignition system, its a mechanical device designed to direct high voltage electricity from the coil to the spark plugs, via the spark plug wires. Rotating the distributor permits adjustment of an engine's initial ignition timing.
Distributor cap   The distributor cap contains the terminals that the spark plug wires plug into. When the distributor sends power to a spark plug, it goes to the cap first and then to the spark plug wire and to the spark plug.
Distributor rotor   The rotor spins around inside the distributor. As it turns, it comes close to the terminals for each spark plug on the distributor cap. When this happens, it sends current to the spark plug, which then ignites the air/fuel mixture in the cylinder at exactly the right time.
Double overhead cam (DOHC)   A DOHC engine has two camshafts in the cylinder head - one for the exhaust valves, and one for the intake valves. This allows greater efficiency and greater power.
Downshifting   The process of going from a higher gear (for instance, fourth gear) to a lower gear (for instance, second gear) with a manual or automatic transmission.
Drive belt   Also called a fan belt or serpentine belt, drive belts are used to drive the engine's accessories, such as the alternator, power steering pump, and air conditioning compressor. A serpentine belt is a wide single drive belt that drives several the engine's accessories at once.
Driveline   The system of components that connects the transmission to the wheels. The driveline consists of axles, differentials, constant velocity (CV) or universal joints, and a driveshaft.
Driver   A switched electronic device housed in a computer that controls output state. For example, a driver controls how long a fuel injector remains open.
Driveshaft   The shaft connecting the transmission output shaft to the differential pinion shaft. It transmits power from the transmission to the differential. It is found primarily on rear-drive vehicles. There is usually a universal joint on either end.

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Early Fuel Evaporation   Used on carburetor-equipped engines only, a system where heat is used to help increase early fuel evaporation of the cold-start air/fuel mixture to achieve more efficient combustion and lower emissions. GM used an electric grid system.
Electric cooling fans   Electric cooling fans are part of many cars' cooling systems. They use a heat activated switch to turn on and off as needed to help keep your engine cool.
Electric motor   Any device that converts Electromagnetic force to motion, or vice-versa. Electric motors are often used in accessories such as power windows or power seats to provide movement with minimal effort by the user.
Emergency brake   Also called the parking brake. A braking system which is independent of the main hydraulic system. It can be used to slow or stop the vehicle if the primary brakes fail, or to hold the vehicle stationary though the brake pedal is not depressed. It usually consists of a foot pedal or hand lever that actuates either front or rear brakes mechanically through a series of cables and linkages.
Emissions   Emissions are the byproducts of combustion. After combustion is complete, water, gases, and carbon are released through the car's exhaust system as emissions.
Emissions equipment   Emissions equipment is equipment required by the government to keep a car's exhaust emissions to a minimum. Emissions equipment includes catalytic converter, air pump, and oxygen sensor.
Engine   A machine designed to convert thermal energy into mechanical energy to produce force or motion. Connected to a drivetrain, an engine's mechanical energy, or torque, moves a vehicle. An engine can run by using gas, diesel fuel, steam or other fuel sources.
Engine accessory   An engine accessory is a peripheral piece of equipment that runs directly off of the engine's power to supply energy or a fluid to another part of the car. Engine accessories include the alternator, power steering pump, air pump, air conditioning compressor, as well as many others.
Engine block   The engine block is where the cylinders and pistons reside. The block is the strongest part of the engine and withstands tremendous pressures while the engine is operating.
Engine mounts   Engine mounts are often made of metal and rubber. Engine mounts help support the engine, and also help to prevent engine vibrations from shaking the entire car.
Engine temperature sender   The engine temperature switch and sending unit measure the temperature of the engine's coolant. They send this information to the engine temperature warning light and engine temperature gauge, respectively. Compare to coolant temperature sensor (CTS) which transmits the coolant temperature to the computer, and the radiator fan switch which engages the radiator's cooling fan.
Evaporative Emissions Control   A system which filters evaporating fuel fumes from the vehicle's fuel system and routes them to the engines intake to be burned.
Exhaust   Gaseous by-products of combustion emitted from an engine. Exhaust flows from the engine, through the muffler and exits from the exhaust system.
Exhaust Gas Recirculation   An engine system where a small portion of exhaust gases are recycled into the combustion chamber. This lowers combustion temperatures and reduces oxides of nitrogen emissions. The EGR system is important for a smooth performing engine.
Exhaust hanger   Exhaust hangers keep the exhaust system in place, while also preventing excess vibration and noise from reaching the passengers.
Exhaust manifold   The exhaust manifold carries the exhaust from the cylinder head to the exhaust system.
Exhaust system   The exhaust system carries exhaust away from the engine and away from the car. The exhaust system includes the exhaust manifold, the catalytic converter, the muffler, and the tailpipe.

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Fan   Designed to supply air flow as the fan blades rotate, a fan can be driven by either a motor or belt.
Fan belt   Also called a drive belt or serpentine belt. Fan belts are used to drive the engine's accessories, such as the alternator, power steering pump, or air conditioning compressor. A serpentine belt is a wide single drive belt that drives multiple engine accessories.
Fan clutch   A viscous-fluid clutch that controls how fast an engine fan rotates to help cool an engine.
Fan motor   An electric motor which drives a fan to direct air, through a radiator or car's interior, for example.
Feedback Carburetor   A computer-controlled carburetor that adjusts the air/fuel mixture according to input from various sensors, via a mixture-control solenoid. The solenoid's adjustment helps maintain the correct air/fuel ratio and minimizes exhaust emissions.
Feeler Gauge   An instrument used to measure the distance between two metal contacts. A feeler gauge could be use to measure spark plug gap, point gap or valve clearance.
Fiberglass matting and resin   These materials are often used to fill in large rust holes where filler would be unable to work, and where welding in new metal would be difficult.
Final Drive Ratio   The ratio between the pinion and ring gear in the drive differential. A numerically high ratio enhances vehicle acceleration and pulling ability, while a numerically low ratio enhances highway cruising and fuel economy.
Flexplate   Secured to the end of the crankshaft, it has three functions; the ring gear for the starter on the outside diameter; helps to balance out engine vibrations; a connection between the transmission torque converter and the engine allowing flexing. Compare to flywheel for manual transmission.
Flushing   Flushing is a means of entirely replacing the fluid in a given system. For instance, when a technician flushes a cooling system, all the old coolant is removed and completely replaced with new.
Flywheel   Secured to the end of the crankshaft, it has three functions; the ring gear for the starter on the outside diameter; helps to balance out engine vibrations; a connection between the transmission clutch and the engine. Compare to flexplate for automatic transmission.
Four-wheel drive (4WD)   A drive system in which both the front and rear wheels are connected through the driveshaft and axles to the transmission, usually via a transfer case. A 4WD sytem can be full time or part time. Sometimes called 4x4 (four by four).
Front-wheel drive (FWD)   A front-wheel drive vehicle sends its power from the engine to the front wheels of the car.
Fuel   Any combustible substance burned to provide heat or power. While gasoline is the most common, other fuels include diesel, ethanol and natural gas.
Fuel filter   A car's fuel filter removes debris and contaminants from fuel before it reaches the carburetor or fuel injection system.
Fuel injection   Fuel injection is a system by which fuel is directly sprayed into the intake manifold or intake port at high pressure. Fuel injection is often controlled by a computer, allowing precise monitoring of efficiency and performance by the car's computer.
Fuel injector   A device for delivering metered, pressurized fuel to the intake system or individual cylinders. An injector sprays fuel, which helps atomization for a more dense mixture, when combined with incoming air.
Fuel pump   The fuel pump moves gas from the gas tank and delivers it to the fuel injection system or carburetor.
Fuel starvation   Fuel starvation occurs when fuel, for one reason or another, is prevented from reaching the carburetor or fuel injectors.
Fuel system   The fuel system is the system by which fuel is stored and delivered to each cylinder. The fuel system includes the fuel tank, fuel tank level sending unit, the fuel pump, the fuel filter, and fuel lines. For carbureted cars, the fuel system also includes the carburetor. For fuel injected cars, the fuel system also includes injectors, fuel pressure regulator and often a main computer.
Fuel tank level sending unit   This unit measures the amount of gas in the fuel tank and sends that information to the vehicle's gas gauge and, if equipped, a low gas level warning light.
Fuses   A device designed to open and protect equipment or a circuit from being destroyed when the circuit is subjected to a power overload. This is a non-reversible action and there are 3 main types of fuses; glass, ceramic and spade.

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G-Force   Unit of measurement used to describe ôlateralö acceleration generated while the vehicle is driven in a steady state turn on a skid pad circle. An average sedan generates 0.60 G of lateral acceleration. Measured in "gravities", one G equals the earth's gravity at sea level.
Gas - grade   This is a general term that refers to a gasoline's general quality - for instance, its octane rating and package of additives. The two common terms for gas grades are "regular" for low-grade gas, and "premium" for high-grade gas.
Gasket   A material usually made of rubber, cork, metal, paper or a combination thereof that is placed between two surfaces to ensure proper sealing against the passage of air, liquid or vapors. Valve cover gaskets are one example of a popular gasket.
Gauge   A gauge is a type of instrument that measures or displays levels of a certain system. For instance, the gas gauge in a vehicle measures the fuel level, while the temperature gauge measures the engine temperature.
Gear selector   The gear selector is the lever that lets you select a certain gear with an automatic transmission. In modern cars, the gear selector is often connected to the brake pedal, so that you can only shift into drive or reverse when your foot is on the brake.
Gear synchronizers   Gear synchronizers allow you to upshift and downshift a manual transmission without grinding gears. They do this by synchronizing, or matching, the speed of the engine and the speed of the gear you are selecting. If your car didn't have gear synchronizers (also known as synchromesh), you would either have to match the engine speed to the gear speed (known as double-clutching) or else grind your gears every time you shifted. See also "synchromesh".
Gearshift lever   The gearshift lever is the lever that allows you select the different gears of a transmission.
Gearshift linkage   This is a series of rods and/or cables that connect the gearshift lever or gear selector to the transmission.
Generator   A generator is like an alternator in that it generates electrical current to both keep the battery charged and supply electricity for a vehicle's electric system. It differs from an alternator in that a generator generates direct current (DC) where an alternator generates alternating current (AC).
Glass Pack   A muffler design that contains fiberglass packing around a perforated internal pipe (straight through) which slightly deadens exhaust noise. Usually louder than a conventional replacement muffler.
Glazing (belts)   Glazing is a shiny coating on the inside surface of a fan, or serpentine belt. Glazing occurs when the belt slips repeatedly at a high speed. It is a sign that the belt needs replacement.
Glow Plug   A combustion chamber heat generating device to aid starting diesel engines. When the glow plug heats the combustion chamber to the proper temperature, the ignition key can be turned to engage the starter.
Governor   An electronic or mechanical device designed to limit engine speed. Large diesel engines usually are equipped with governors.
Ground   An electrical conductor used as a common return for completing an electric circuit(s). Car batteries contain a ground terminal, usually the negative terminal.

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Halfshaft   An exposed axle driveshaft usually having a CV (constant velocity) joint on either end, being driven from a differential. Also called a CV axle.
Hazard relay   The hazard relay controls the flashing of the hazard warning lights.
Head gasket   The head gasket seals the cylinder head to the engine block. It is subject to tremendous pressures, and often fails if and when an engine overheats.
Headers   Constructed from steel tubing, headers provide a smooth and efficient exhaust flow path from the exhaust port to the exhaust system. Headers are frequently used in performance engine applications and are generally less restrictive than the stock exhaust manifold, resulting in increased power.
Heater core   The heater core is a miniature radiator that sits in the dashboard area. When the heater is turned on, it opens the heater valve which lets hot coolant into the heater core, which then warms the air coming into the vehicle's interior.
Heater ducts   The heater ducts are the passageways through which warmed air enters the interior of the vehicle.
Heater fan   The heater fan is the interior fan attached to a blower motor that controls the speed of air being introduced into the interior.
Heater valve   The heater valve is controlled by the interior heating controls. When you turn on your vehicle's heater, the valve opens and allows hot coolant to enter the heater core, which then warms the air forced through the heater core by a blower motor, and the warmed air then enters the vehicle's interior.
Heater/heating system   The heating system warms the air brought into a vehicle's interior. The heating system is connected to the cooling system and consists primarily of the heater core, heater valve, and, if equipped, a climate-control system.
Hex Wrench   Also known as an Allen wrench, it is a hexagonal tool that fits and operates fasteners with hexagonal openings.
Hoses (cooling system)   The cooling system hoses allow coolant to circulate between the radiator, engine, and heater. Over time, they deteriorate, and should be checked annually for condition and possible damage.
Hub   Hub is a generic term for a circular area where a component is mounted. For instance, there are hubs for every wheel on your car.
HVAC   Stands for Heating, Ventilation, Air Conditioning. These systems are controlled by the car's climate control panel.
Hydraulic circuit   The hydraulic circuit is a closed system of tubes and components that contain hydraulic fluid. When pressure is applied at one end of the hydraulic circuit, it travels through the tubes to the other end.
Hydrocarbon   An organic compound containing various carbon and hydrogen molecules linked together in fuel. Gasoline is a hydrocarbon fuel. If the fuel is not burned efficiently in the cylinders, hydrocarbon molecules are released into the atmosphere as pollutants.

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Idle   Running engine speed with vehicle at rest and accelerator or throttle pedal not depressed. While waiting at a stop light, the engine is at idle.
Idle circuit   This is a special kind of circuit found in a carburetor that only operates when the engine is at an idle.
Ignition   Complete system used to step up battery voltage to a higher voltage and deliver it to the spark plug to complete the combustion process. When the key is turned on, the ignition system is energized.
Ignition Advance/Retard   The advancing or retarding (in crank degrees) of ignition spark relative to the piston location in the cylinder. Ignition timing should be set to factory specifications.
Ignition condenser   The condenser collects and stores excess electrical energy in an older ignition system that has points. This prevents that extra energy from jumping across the points when they first open and close.
Ignition module   Part of the ignition system which instructs the ignition coil to send current to the distributor.
Ignition points   Part of the ignition system which allows the ignition coil to send current to the distributor in older vehicles. Ignition points do this by opening and closing, which opens and closes the electric circuit. Electronic ignition systems have made ignition points and condensers obsolete.
Ignition switch   This is the switch where you insert the key that starts the vehicle.
Ignition system   The ignition system contains the components that supply spark to the vehicle's spark plugs. These include the battery, the ignition coil, the distributor (including the cap and rotor), the spark plug wires, the ignition module, and the spark plugs themselves. Older cars also have ignition points and an ignition condenser.
Injector (fuel)   A device for delivering metered, pressurized fuel to the intake system or individual cylinders. A fuel injector sprays fuel, which helps atomization for a more dense mixture, when combined with incoming air.
Instrument   An instrument measures levels of a certain system and provides a visual key for those levels. For instance, the gas gauge in your car measures the fuel level, while the temperature gauge indicates the engine temperature.
Intake Air   Air used in combustion that flows through an air filter, throttle valve and is distributed to each cylinder by the intake manifold.
Intake manifold   The intake manifold is located between the vehicle's fuel system and the cylinder head(s) to distribute the fuel/air mixture to individual cylinders.

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Knock (Engine)   The sharp, metallic sound produced when two pressure, or flame fronts collide in the combustion chamber. This could be the result of incorrect ignition timing or the wrong grade (octane rating) of gas. Higher octane fuel can eliminate knock due to its increased resistance to cylinder pressure.

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Lathe   Device used to machine the outside and/or inside of a metal object as it rotates. A brake lathe is used to smooth the exterior pad surface of a brake rotor or the interior of a brake drum.
Leaf Spring   A thin, long, arched, steel spring that is attached between a vehicleÆs frame and axle to act as a suspension. More than one spring leaf are often clamped together to achieve a desired load capacity or spring rate.
Leakdown test   A leakdown test is used to find excessive wear in an engine. When a technician performs a leakdown test on a vehicle, each cylinder is tested to see how well it holds pressure. If a cylinder is unable to hold pressure, your technician can pinpoint what component of the cylinder (piston rings, valves, etc) has the problem that is causing the pressure loss.
Liability insurance   Liability insurance is coverage only for damage that you inflict on other people or their possessions. It does not cover theft or damage to your vehicle.
Limited-slip differential (LSD)   An LSD senses the slippage of each wheel and sends and redirects power to the wheel with the most grip. Many high-performance vehicles have LSDs.
Link (Electrical/Electronic)   General term used to indicate a communication connection between two data points. Mechanics use a link to retrieve trouble codes from a vehicle's ECU in order facilitate repairs.
Linkage   A series of bars, levers, yokes, rods, or cables used in unison to transmit motion from one unit to another. Transmission shift linkage connects the shifter to the transmission and allows gear selections to be made.
Loaded (caliper)   A disc brake caliper, which comes complete with all the installation hardware such as emergency brake lever, spring, bracket and brake pads. This speeds a caliper installation during replacement.
Lug nuts   Lug nuts attach a car's wheel to its hub. Also known as wheel nuts.

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MacPherson strut   A shock absorbing component in a front suspension system that is mounted directly above the upper control arm. Many lightweight, uni-body cars use this uncomplicated type of front suspension.
Main Bearings   Soft metal alloy inserts, bonded to a steel back, used to allow the crankshaft to ride on a cushion of oil formed between the crank journal and bearing surface. Main bearings often last throughout the life of the engine.
Manifold   A component designed to collect and/or distribute an engine's air and/or fuel mixture, or exhaust.
Manual choke   A manual choke system has a cable that lets the driver control the carburetor's choke operation. Most newer cars with carburetors have automatic chokes instead of manual chokes.
Manual steering   With a manual steering system, there is no power assist to the driver.
Manual transmission   A manual transmission is a transmission with a clutch. In addition, it is up to the driver to select gears.
Memory   A device in which data can be stored and retrieved when needed; associated with a vehicle's computer system.
Mode   One of several alternative conditions or methods of operating a system, device or control module. If a vehicle has a 3-mode electronic adjusting shock absorber system, the modes (or settings) are usually soft, medium, or firm.
Module (Electrical/Electronic)   A self-contained group of electrical/electronic components, which is designed as a single replaceable unit. An example of a module is the one that operates the anti-lock braking system.
Muffler   The muffler is a part of the exhaust system designed to reduce the noise generated by a vehicle.

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Neutral (gear)   Neutral is actually not a gear. When your vehicle is in neutral, the gearbox (transmission) and engine are completely disconnected. Thus, your car is able to roll freely whether the engine is on or off.

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Octane   A fuel octane rating measures a fuel's resistance to knocking or pinging. The higher the octane rating, the better (and more expensive) the fuel.
Odometer   The odometer measures how many miles your vehicle has traveled.
Oil filter   The oil filter removes most particles and contaminates from your engine's oil to protect your engine's internal moving parts.
Oil pan   The oil pan is where the oil in your engine is stored.
Oil pressure sensor   The oil pressure sensor measures the pressure at which your engine's oil is flowing. If the pressure becomes too high or too low, the oil pressure sensor sends a signal to the vehicle's oil pressure warning light located on the dashboard. If you see this light turn on, pull over as soon as possible and shut off your engine. Check the oil level of the engine by pulling out the dipstick. If the engine oil level is low, add oil, restart the vehicle and see if the oil light goes out. If the oil level is within parameters, or the oil light remains on, have your car towed to a service facility to have the problem checked by a technician.
Oil pump   The oil pump takes oil from the oil pan and pressurizes it, allowing it to travel throughout the engine and lubricate the engine's moving parts.
Open Loop   An operating condition or mode in the vehicle's intake fuel system controlled by the vehicle's PCM, based on pre-programmed instructions, usually when an engine is in the cold start-up mode.
Output Shaft   A shaft that drives the next element in the powertrain, like the front driveshaft yoke slipping over the output shaft of the transmission, which drives the wheels.
Overboost (turbo)   Overboost occurs when a turbo's wastegate does not release excess intake pressure. This pressure instead enters the engine, causing potentially significant damage to the engine.
Overdrive   Overdrive is a transmission gear that allows the engine to turn at a reduced rpm for a given road speed.
Overhead cam (OHC)   An overhead cam engine has its camshaft in the cylinder head, above the valves and cylinders. This allows the camshaft to directly open the valves without using pushrods.
Overhead valve (OHV)   An overhead valve engine has its camshaft in the engine block. It uses lifters, pushrods and rocker arms to open and close the valves in the cylinder head.
Overheating   Overheating occurs when an engine reaches too high of an operating temperature. Overheating may lead to potentially significant engine damage.
Overinflation (tires)   Overinflation occurs when a tire is inflated beyond the pressure recommended by the manufacturer. Overinflating can lead to increased tire wear and sudden tire failure.
Owner's manual   The owner's manual is the booklet supplied with all cars when they are sold new. It is usually placed in the glovebox. The owner's manual contains information about the vehicle's equipment and options, what kinds of fluids and lubricants to use, and how to maintain your car. If you don't have an owner's manual, one can be obtained from the vehicle's manufacturer.
Oxides of Nitrogen   Commonly known as NOX, it is various combinations of one part nitrogen and one or more parts of oxygen, which is a by-product of combustion at a very high temperature when using gasoline as a fuel. NOX is a component of smog.
Oxygen sensor   The oxygen sensor is part of the exhaust and emission systems and is usually located in the exhaust manifold. It senses the amount of oxygen in the exhaust gases and adjusts the fuel system's operation accordingly to minimize emissions while improving economy and performance.

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Park (gear)   This is a gear found only on automatic transmissions. The park gear locks a vehicle's transmission in place, preventing the car from moving.
Park/neutral safety switch   This is a switch found on many modern automatic transmissions that prevents a vehicle from starting unless the gear selector is in park or neutral.
Parking brake   Also known as the emergency brake. The parking brake is used when parking on an incline to prevent the car from rolling away. The parking brake is usually cable operated and can be used as a backup if the regular hydraulic brake system fails.
Parking brake cable   The parking brake cable connects the parking brake pedal or handle to the parking brakes themselves.
Parking brake shoes/pads   The parking brake shoes/pads are just like normal brake pads or brake shoes. The only difference is that they work specifically with the parking brakes, and are independent from the regular brake system.
Petcock   A small valve used for draining liquids. Petcocks are usually associated with radiators and are located at the bottom of one of the radiator's tanks.
Pinging (engine)   A noise made in the engine caused by a pre-ignition condition. When your engine knocks or pings, it is a sign that the engine is firing at the wrong time. This could be because of improper ignition timing, an incorrect grade of gas, or another ignition or fuel system fault.
Piston   An aluminum-based cylindrical part located inside an engine's cylinder (combustion chamber) that moves up and down, transferring the force of combustion to the connecting rod and then to the crankshaft, which causes rotation.
Piston Ring   Usually 3-4 rings that fit on the outer diameter of the piston beneath the piston top which seals the pressure of combustion in the cylinder (top 2 or 3 rings called the compression rings) and aids in scraping residual lubricating oil from the cylinderÆs walls (bottom ring called the oil ring).
Piston-To-Valve Clearance   The distance or space between the intake and exhaust valves in relation to the top of the piston when the piston is at the top of its stroke, known as TDC, or top dead center.
Pitman Arm   Arm attached to the pitman shaft on a steering box that moves the relay rod as the steering wheel is turned in a mechanical (not rack and pinion) steering system..
Plastic polish   A special type of polish designed to gently remove scratches and yellowing from plastic items such as convertible top windows and plastic lenses.
Play   Play occurs when there is excessive free movement in a vehicle's steering system. For instance, if you turn your steering wheel either direction from the center and nothing happens for the first two inches of travel, your steering system has play in it.
Porting   The enlarging of the exhaust and intake passages to increase flow through the cylinder head. When done correctly, this process can add a significant amount of power and increase fuel efficiency.
Posi   Also known as Positraction, which is a limited-slip differential (LSD) distributing power equally to both drive axles through a series of plates, clutches and springs.
Positive Crankcase Ventilation (PCV)   This system relieves pressure and recirculates fumes created by the motion of the crankshaft, connecting rods and pistons in the crankcase, by sending them through a one-way valve back into the engine to be burned in the combustion process.
Power Steering   A system which provides additional hydraulic force, generated by a pump, to the steering mechanism, either a steering box or rack, reducing the driver's turning effort at the steering wheel.
Power steering fluid   A special type of fluid designed for power steering systems.
Power steering pump   The power steering pump transfers power steering fluid under pressure to other power steering system components, allowing the driver to steer with minimal effort.
Powertrain   The elements of a vehicle by which motive power is generated and transmitted to the driven axles. Examples of powertrain components are the engine, transmission and differential.
Powertrain Control Module (PCM)   A module commonly referred to as the vehicle's "main computer", it controls how the engine and transmission operate via input from many sensors. Aka: ECM (Electronic Control Module), EEC (Electronic Engine Control) and ECU (Electronic Control Unit).
Prechamber   A dual-chamber combustion system for diesel engines with a centrally located auxiliary combustion chamber for reduced emissions and less diesel soot.
Pressure (Absolute)   The pressure referenced to a perfect vacuum, usually found in the intake manifold. Commonly known as the MAP, or Manifold Absolute Pressure.
Pressure (Atmospheric)   The pressure of the air outside of the engine at any given temperature and altitude. Sometimes called barometric pressure, it is usually referenced as the "baro" sensor reading in the powertrain control system.
Pressure (Differential)   The pressure difference between two areas in the engine, such as between the pressure in the intake manifold and the atmospheric, or outside, air pressure.
Pressure Plate   The part of a manual clutch system with a covered spring and clamping ring mounted over the friction disk, to the flywheel. When the pressure plate is engaged, it clamps the friction disk to the flywheel, which turns the input shaft of the transmission. It allows the smooth application of power to the transmission. Also known as a clutch cover.
Primer   A type of paint applied to a vehicle's surface to increase its compatibility with the topcoat and/or to improve the corrosion resistance of the base metal. The primer paint is applied first, then the final topcoat, or color coat of the vehicle is applied on top of the primer coat.
Proportioning Valve   A valve in the brake hydraulic system usually located in or near the brake master cylinder that controls pressure to the rear wheels to achieve better braking balance front-to-rear.
Pump   A device used to transfer fluids or air by suction, pressure, or both. An example of this is an oil pump for the vehicle's engine, or the pump that raises and lowers the air pressure in a vehicle's air-ride suspension system.
Pushrod   Pushrods are used in engines with overhead valve (OHV) designs. The camshaft in the engine block pushes up on the lifters and then on the pushrods, which then push the rocker arms, which then open the valves.

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Radial   Referring to a type of air conditioning compressor that compresses its refrigerant using a radial, or round, piston and cylinder arrangement. It's a fairly light unit and is associated with 1982 and newer GM vehicles and used R12 and R-134 refrigerant. Compare to Axial. (Remember, Axial is LONG like an axle; Radial is SHORT like a radial tire.)
Radiator   A radiator is a liquid-to-air heat transfer device having a tank(s) and core(s) specifically designed to reduce the temperature of the coolant in an liquid-cooled internal combustion engine. Radiators can be made from aluminum or copper-brass.
Radiator cap   The radiator cap maintains a specific pressure in the cooling system so it operates efficiently.
Rail   A manifold for fuel injection which distributes fuel to the fuel injectors, often called a fuel rail. They are usually made from an aluminum extrusion or steel pipe.
Ram Air   Type of induction where fresh air is fed through the hood or underneath the vehicle and sent to the intake via the air filter. With the reduced air temperatures associated with fresh, non-underhood, ram air, more power and efficiency is generated.
Rear-wheel drive (RWD)   Rear wheel drive cars transmit power to the ground through the rear wheels.
Refrigerant   Commonly referred to as freon, it is a substance used as a heat transfer agent in an air conditioning system. There are two types being used in vehicles today; R134 for newer cars and R12 for older vehicles. Because R12 refrigerant is harmful to the environment when it leaks into the atmosphere, it is being phased out in favor of R134.
Regulator (Voltage)   A device that automatically controls the output of another device by adjusting the voltage to meet a specified value. Example: an alternator can put out over 14 volts, but by sending the voltage through a regulator, it only allows 12 volts output.
Relay   A electromechanical device in which connections of a higher voltage circuit are operated by a lower voltage circuit to divert the current. High-output auxiliary driving lights contain relays in their circuits so as not to overload and burnout the on-off switch.
Remanufactured   A component or piece of equipment that has been rebuilt and restored to its OE (original equipment) specifications to function as new. Common examples of rebuilt parts include alternators, water pumps, carburetors and power steering pumps.
Reservoir   Reservoir is a generic term that refers to any container for a fluid. For instance, most vehicles have a windshield washer fluid reservoir and a brake fluid reservoir.
Revving the engine   Increasing the RPM's of an engine without allowing the power to be transferred to the wheels. When your car is in park or neutral and you press on the gas without the intention of making the car move, you are revving the engine.
Rheostat   Rheostat refers to a control which varies the intensity of the lights and speed of certain accessories that it is connected to. For instance, an instrument lighting rheostat controls the brightness of the instrument lighting.
Riding the clutch   When driving along, if you rest your foot on the clutch pedal, you are riding the clutch. This practice causes excess wear on the clutch and the clutch throw-out bearing.
Rocker arms   Rocker arms are used in overhead valve (OHV) engines. They are operated by pushrods and open and close the valves.
Roller Cam   A camshaft which uses lifters, either hydraulic or mechanical, using rollers at the base of each lifter which contacts the cam. These high-strength steel cams reduce friction and emissions and increase power and efficiency with optimized lobe designs.
Rotary engine   A rotary engine does not have pistons or cylinders; instead, it has triangular shaped rotors that move in an elliptical path within chambers to create power. The only companies that have offered rotary cars for sale are Mazda, NSU, and Citroen.
Rotor- Brake   A disc made from cast iron or steel, rotating on an integral or separate hub near the wheel of a vehicle and is stopped by friction pads located on either side of a hydraulically-operated brake caliper.
Rotor-Distributor   An electrically conductive component mounted to the rotating distributor shaft that transfers electrical energy from the centrally located coil terminal to the individual cylinder terminals within the distributor cap circumference. Also known as an ignition rotor.
Rubbing compound   A rubbing compound is a type of paint polish that contains extremely fine abrasive particles. These particles remove the top layer of paint, eliminating shallow scratches, and revealing the shiny paint layer underneath.
Running Board   Usually a long, flat board that runs along the rocker panel of a truck or SUV, which is used to help passengers step in and out of the vehicle.
Running rich   This is a condition that occurs when too much gas and too little air is being fed to the engine. A sign of rich running is black, sooty exhaust.
Rust-converting primer   Rust-converting primer is a special type of primer paint that stops the progress of surface rust.

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Scan Tool   A device that interfaces with, and communicates vehicle information to and from a vehicle's powertrain control module or computer, via an onboard data link.
Sensor   The name for a device that senses the absolute value or a change in a physical quantity such as temperature, pressure, rotation or flow rate, and converts that change into an electrical signal, which is then sent to the vehicle's powertrain control module (PCM).
Serpentine belt   A serpentine belt is a wide single drive belt that drives certain engine accessories (alternator, power steering pump, air conditioning compressor, etc.). It's a type of fan belt with multiple grooves that fit into similar grooves on the pulleys. Also know as a multi-groove belt, micro-groove belt, or multi-v belt.
Shift linkage   This is a series of rods and/or cables that connect the gearshift lever or gear selector to the transmission.
Shift Solenoid   A PCM-controlled electromechanical device which regulates shift firmness and rpm in an electronically-controlled automatic transmission.
Shock Absorber   A component using friction to dampen and control a vehicle's suspension up and down movement. Modern shocks are of the hydraulic type, using an oil to dissipate the heat of friction to the outside air. They contribute to your vehicle's ride quality. See also Strut.
Short (circuit)   A short circuit occurs when there is a break in an electrical circuit and the circuit finds a new ground source.
Shroud   A metal or plastic cover used to isolate rotating components or hot parts of the vehicles' engine or exhaust system. A radiator shroud surrounds the radiator fan and helps direct incoming air through the radiator and to the front of the engine as well as protecting the radiator and fan from foreign objects.
Single overhead cam (SOHC)   A type of overhead cam engine with a single cam that operates both the intake and exhaust valves.
Solenoid   A device consisting of an electrical coil, and when energized, produces a magnetic field in a plunger and is pulled to a central position. A solenoid may be used as an actuator in a valve or switch. Power door locks use a solenoid-activated actuator.
Spark Plug   Part of the ignition system, it's an electrical device with a ground and center electrode where a spark is created between the two by a high voltage current from the distributor. The spark ignites the fuel/air mixture in the combustion chamber at the top of the compression stroke.
Spark plug electrode   The electrode is the curved piece(s) of metal (ground electrode) that reaches over the center electrode. The spark is created between the electrodes.
Spark plug gap   Gap is the precise distance between a spark plug's center and ground electrodes.
Spark plug terminal   The terminal is the metal part of a spark plug above the ceramic insulator that the spark plug wire attaches to.
Spark plug wires   Spark plug wires are the cables that conduct the electric pulses from the distributor cap to the spark plugs. Also called ignition wires.
Speedometer   An instrument that indicates a vehicle's speed in miles or kilometers per hour.
Sprag   A transmission internal component load carrying element, usually consisting of roller bearings and a cage element. Heavy duty sprags have more bearings, therefore a greater load capacity.
Springs (suspension)   Springs absorb road imperfections and vibration, help hold the suspension up, and help vehicles handle better. Also called coil springs, or leaf springs.
Stabilizer bar   See Sway bar.
Starter motor (starter)   This is the electric motor that turns your engine over when you turn the key in the ignition switch.
Starter solenoid   This is a large relay that controls the operation of the starter motor.
Starting system   The starting system consists of the starter motor, starter solenoid, battery, ignition switch and ignition key.
Steering lock   The steering lock is a theft prevention device that locks the steering wheel in place when the key is removed from the ignition switch.
Steering system   The steering system allows you to control the direction of your vehicle. Most modern cars have a rack and pinion steering system with a power assist. Components in your steering system include the steering rack, tie rods, tie rod ends, ball joints, power steering pump, power steering hoses, and the pump drive belt.
Stroke   The distance traveled by the piston in its cylinder from top dead center to bottom dead center. The stroke is determined by the throw of the crankshaft, and is a determining factor in the displacement of an engine.
Struts   Struts are part of your vehicle's suspension, and do the same job as a shock absorber. A vehicle will either have struts or shock absorbers, or a combination of both (i.e. struts in the front, and shock absorbers in the rear). They regulate how much your vehicle can move up and down, and keeps the tires in contact with the road surface after going over a bump.
Supercharger   A mechanically driven device, usually off the crankshaft, that pressurizes the intake air, and in turn increases the density of the air/fuel mixture and subsequently increases the power output of a given engine displacement.
Suspension   The suspension connects the vehicle body to the frame. A well tuned suspension helps the vehicle to handle better, while increasing comfort and isolating passengers from bumps and vibration.
Sway bar   The sway bar is a suspension system component that helps to minimize the lean of a vehicle when cornering. Also called a stabilizer bar.
Synchromesh   Synchromesh is a feature that allows you to upshift and downshift a manual transmission without grinding gears. It does this by synchronizing, or evening out, the speed of the engine and the speed of the gear you are selecting. If the transmission didn't have synchromesh, you would either have to match the engine speed to the gear speed (known as double-clutching) or else grind the gears every time you shift. This term is often shortened to just "synchro".

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Tachometer   An instrument that indicates engine speed in revolutions-per-minute (rpm). It measures the speed that the crankshaft is rotating.
Tailpipe   The part of an exhaust system where exhaust gasses exit the car body from the rear of the vehicle. The tailpipe connects the muffler to the tailpipe tip (sometimes called a spout). The tailpipe tip is the part of the exhoust system that you can see sticking out from under the rear bumper.
Thermostat   The thermostat is a valve located in the cooling system of a vehicle that automatically regulates the coolant flow through the radiator and engine based on the coolant temperature.
Throttle   A mechanism for regulating the supply of the fuel/air mixture to an internal combustion engine, thereby regulating the speed of the engine. Aka; accelerator pedal
Tie rod   Part of the steering system, the tie rod connects the spindles/wheels to the rest of the steering system.
Timing (ignition timing)   Timing refers to the moment when the spark ignites the air/fuel mixture in the engine's combustion chamber. Timing needs to be set exactly right for an engine to run correctly.
Timing belt   Timing belts are rubber belts that connect an engine's camshaft to its crankshaft. If a timing belt breaks, these two components will get out of synch, which can cause potentially significant engine damage.
Timing chain   Timing chains are metal chains that connect an engine's camshaft gear to its crankshaft gear. Timing chains ride on sprockets that eventually wear out and can cause sloppy timing. When this happens, it is time to replace the sprockets and chain. If a timing chain breaks, the camshaft and crankshaft will get out of synch, causing potentially significant engine damage.
Timing gears   Timing gears are part of a timing chain system that connects the engine's camshaft to its crankshaft. On some vehicles, the camshaft gear meshes directly with the crankshaft gear, eliminating the timing chain.
Timing light   A timing light is used to check or set ignition timing.
Tire gauge   Tire gauges are used to measure the air pressure of a tire. You should always check tire pressure when your tire is cold (when the vehicle hasn't been driven for about an hour).
Tire valve   The fitting in the valve stem of the wheel that allows you to inflate or deflate the tire.
Tonneau   An accessory cover fitted to protect a vehicle bed or driver's compartment, most often on pickups and early autos. A tonneau can be constructed of fabric, metal or fiberglass. In addition to sealing the vehicle bed or passenger area, it also contributes to vehicle appearance.
Torque converter   A fluid coupling device which multiplies torque between an engine and automatic transmission/transaxle. It allows smooth power transfer from the engine to the transmission. When a vehicle is stopped, a converter allows enough fluid slippage so that the engine can idle without stalling.
Transaxle   Transaxles are a combination of components; the transmission and differential. Most front-wheel drive cars have transaxles. However, some rear wheel drive cars, such as some Porsches, new Corvettes and Alfa Romeos, have rear-mounted transaxles.
Transducer   A device that receives an electrical signal from one system and transfers it, often in a different form, to another system. Example: the cruise control transducer converts a vehicle speed signal to a vacuum to control the servo attached to the throttle.
Transfer case   Used in 4X4 vehicles to transfer power to the front and rear differential assemblies. There are different selectable ranges to maximize traction in varying road or trail conditions.
Transmission   A component of the powertrain of a vehicle which selects gear changes (either manually or automatically), which can increase or decrease the speed and power between the engine and the drive axles.
Transmission fluid   Transmission fluid (ATF) is specially developed to allow automatic transmissions operate smoothly and efficiently. Automatic transmission fluid needs to be checked and replenished periodically.
Transmission interlock   A safety device found on many modern automatic transmissions that prevents the drive or reverse gear from being selected until the brake pedal is pressed.
Transmission linkage   This is a series of rods and/or cables that connect the gearshift lever or gear selector to the transmission, allowing the shifting of gears.
Transmission mounts   Transmission mounts are often made of steel and rubber. Transmission mounts help support the transmission, and also help to prevent transmission vibrations from being transmitted to the car interior.
Transmission oil   Transmission oil is specially developed to allow manual transmissions to operate smoothly and efficiently. Transmission oil rarely needs to be replenished.
Travel   Travel is a measurement of how much movement, or play, occurs in a given system.
Trinary   Consisting of three (3) parts, or a progression of a multiple of threes (3).
Tune up   A proceedure during which a series of parts that wear out (spark plugs, ignition rotor, distributor cap, etc.) are replaced to bring the engine back into proper operating specifications. In addition, timing is normally checked and reset. A tune up is usually performed according to a schedule.
Turbocharger   A centrifugal device driven by exhaust gases that pressurizes the intake air, increasing the density of the air and consequently increasing the power output from a given engine displacement. A turbocharger will boost the power of an engine. Aka turbo.

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Universal joint   Universal joints are part of a car's driveline. They allow the driveshaft to continue to rotate at all angles.

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Vacuum   A condition in which pressure has been reduced below the ambient atmospheric pressure. Vacuum is created in the intake manifold and can be used to operate a power brake booster.
Vacuum hose   Vacuum hoses connect between vacuum-powered accessories and a vacuum source such as the engine's intake manifold.
Valve   A device by which the flow of a liquid, gas or vacuum may be controlled. Example: the intake and exhaust valve in the cylinder heads start and stop the flow of the incoming fuel mixture and outgoing combusted exhaust gases.
Valve cover   The valve cover is the metal cover that is attached to the top of the cylinder head. It allows technicians access to the engine valves and rocker arms for adjustment and checks.
Valvetrain   Components actuated by the camshaft and can include valve lifters, pushrods, rocker arms and valve springs.
Vapor lock   Vapor lock occurs when an engine gets so hot, it boils the fuel traveling through the fuel lines. This creates vapor, preventing the fuel from traveling through the lines, causing the engine to stop running.
Variable-assist power steering   A power steering system designed to vary the level of power assist according to vehicle speed or angle of the steering wheel.
Voltage regulator   The voltage regulator limits the power output of the alternator to prevent overcharging the battery and electrical system.

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Washer fluid   This is special fluid designed to help clean the windshield quickly and with little residue, used in conjunction with the wiper blades.
Washer fluid reservoir   The container where washer fluid is kept in a car, usually located under the hood.
Washer nozzles   These are the jets on the hood or in the wipers that spray washer fluid onto the windshield.
Washer pump   An electric motor that delivers washer fluid to the washer nozzles for cleaning the windshield with the windshield wipers.
Wastegate   A valve on a turbocharged engine that limits air pressure in the intake tract by allowing the pressure to bypass to outside air, after the turbocharger.
Water in fuel warning light   This is a warning light found only on diesel-engined cars. Because diesel fuel collects water, a sensor in the fuel tank will indicate when the ratio of diesel fuel to water reaches a certain level.
Water pump   Part of the cooling system, the water pump circulates coolant, helping the engine to stay in the desired temperature range.
Wax   Wax is a product used to protect paint finishes and create extra shine.
Weather-stripping   A rubber gasket found around vehicle openings to seal out water and wind. Weather-stripping is located around doors, windows and trunks.
Wheel bearing   A bearing or bearing assembly located at each wheel allowing the wheel to spin around the axle with minimal wear and friction. Front wheel bearings are contained within the hub, and are sometimes integral to the hub. A wheel bearing set consists of an inner and outer bearing.
Wheel cylinder (brakes)   The wheel cylinder is used with drum-type brakes. When the brake pedal is pushed, the wheel cylinder pushes the brake shoes against the drum brake, slowing or stopping the car.
Wheel nuts   Wheel nuts are used to attach a wheel to a hub.
Wiper arms   The part of the windshield wipers that are between the wiper pivots at the base of the windshield and wiper blades.
Wiper blades   The rubber part and carrier assembly of the windshield wiper that clears the windshield.
Wiper refill   The rubber part of the wiper blade that makes contact with the windshield. A wiper refill will insert into a wiper blade.
Wire (electrical)   An insulated conductor used in an electrical system to transmit electricity from one component to another. If a wire breaks, it creates an open circuit. If a broken wire make contact with a grounded surface, it creates a short circuit.

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