Emissions

• Catalytic Converter - A pollution-control device found on the exhaust system of all cars since its introduction in 1974 which acts like an afterburner to re-burn unburned gas in the tail pipe to reduce emissions.  It looks like a small muffler and is usually made of stainless steel.
• EGR Valve and System - An emission control system where some of the exhaust gases are rerouted from the exhaust manifold into the combustion chamber to control smog.
• Oxygen Sensor - A device that detects the amount of oxygen in the exhaust stream and sends that information the ECM for proper fuel control.
• ECM or PCM - Acronym for "Electronic Control Module", which is the master computer responsible for interpreting electrical signals sent by engine sensors and for activating automated engine components and processes accordingly in order to produce optimum performance.
• Canister Purge Control Valve - Valve used to regulate the flow of vapors from the evaporative canister to the engine.
• PCV Valve - A one-way valve which controls the flow of vapors from the crankcase into the engine.
• Air System - An emissions system to inject fresh air into the exhaust system to reduce emissions.

• Wires - A way to deliver high-voltage to the spark plugs.  They are composed of either copper core or carbon core with thick insulation.  It comes from the distributor to the spark plug.  Also called an ignition cable.
• Spark Plugs - A device containing two electrodes across which electricity jumps to produce a spark to fire the fuel charge.
• Distributor Cap and Rotor - A unit in the ignition system designed to make and break the ignition primary circuit and to distribute the resultant high voltage to the proper cylinder at the correct time.  The high voltage comes from the coil to the center terminal of the distributor cap and passes down the rotor.  As the rotor turns, contact is made with each successive terminal on the circumference of the distributor cap.  From there, the voltage goes into the spark plug wires and to the spark plug.  Generally when your vehicle has its timing adjusted, it is the distributor that is adjusted. Also called "ignition distributor."
• Ignition Coil and Module - The standard ignition system which uses an ignition coil which stores the power from the battery and steps it up. Then the high voltage is sent to the spark plugs.
• Fuel Filter - A device that removes impurities from the fuel before it gets to the fuel injectors.  It is usually found in the fuel line that comes from the fuel pump.  This unit must be cleaned or replaced on a regular basis, usually once a year, or it will become clogged and restrict fuel flow.  This can cause damage to the fuel pump.
• Fuel Pump - A vacuum device, operated either mechanically or electrically, that is used to draw gasoline from the tank and sends it into the carburetor or fuel injector nozzles.
• Fuel Injectors - A fuel system that uses no carburetor but sprays fuel either directly into the cylinders or into the intake manifold just ahead of the cylinders, controlled by the ECM to deliver the correct amount into the combustion chamber.  Throttle-body injection locates the injector(s) centrally in the throttle-body housing, while port injection allocates at least one injector for each cylinder near its intake port.
• Intake Manifold - The connecting tubes between the base of the carburetor and the port openings to the intake valve or intake ports.  The air-fuel mixture travels from the throttle body into a chamber called the plenum, which feeds individual tubes (called runners), which lead to the individual intake port.  Its purpose is to transfer the air-fuel mixture to each cylinder.
• Throttle Body - A housing containing a valve to regulate the airflow through the intake manifold.  The throttle-body is usually located between the air cleaner and the intake plenum.
• Scope (Scope Check) - A testing unit, which projects visual reproduction of the ignition system spark action onto screen of cathode-ray tube.
• Computer Command Controls (CCC) - An electronically controlled fuel metering system used on GM vehicles.  Uses an oxygen sensor, a throttle position sensor and other information sensors to provide a computer with the data it needs to alter the air/fuel ratio via mixture control solenoid in the carburetor.
• Idle Air Control (IAC) Motor - (IAC) Used to control idle speed on fuel injection vehicles.  A valve that allows air to bypass the throttle plate(s) increasing idle speed.  The valve is operated by an electric solenoid or motor.  The vehicle computer controls the amount of opening to regulate idle speed for varying conditions such as cold start and air conditioner compressor load.

• Master Cylinder - The part of the hydraulic brake system which stores the brake fluid.  As the brake pedal is applied pressure is forced against a small movable piston in the master cylinder to push hydraulic fluid through the brake lines to the wheel cylinders and force the brake linings against the drum (in the case of drum brakes) or force the brake pads against the disc (in the case of disc brakes).
• Brake Pads and Shoes - The friction material or lining, which is secured to metal plates.  They press against the brake disc or rotor to enable the wheel to stop.  They are to be distinguished from brake shoes, which press against the inside of a drum.
• Brake Shoes - That part of the brake system, located at the wheels, upon which the brake lining is attached.  There are usually two shoes (curved or arc-shaped pieces) in each wheel.  When the wheel cylinders are actuated by hydraulic pressure they force the brake shoes apart and bring the lining into contact with the brake drum.  In this way the vehicle is slowed or stopped.
• Brake Rotors - The brake disc, which is attached to the wheel and is surrounded by a brake caliper.
• Brake Drums - A cast iron or aluminum housing bolted to the wheel that rotates around the brake shoes.
When the shoes are expanded, they rub against the machined inner surface of the brake drum and exert a braking effect upon the wheel to slow or stop the vehicle.
• Wheel Cylinders - A small cylinder located at each wheel brake that uses brake fluid to exert hydraulic pressure, which forces the brake shoes against the brake drums and stops the vehicle.
• Parking Brake Cables - A wire cable, which activates the brakes and used for the parking brake.
• ABS - A system, which senses that one or more of the wheels are locking up during braking.  It monitors the rotational speeds of the wheels and reduces hydraulic pressure to any wheel it senses locking up.  This allows for maximum control to be maintained while braking.  It is controlled by both mechanical and electronic components.  When you apply the brakes, the ABS will regulate the flow of brake fluid being delivered to the brake calipers.  By the use of electronic computers, the brakes rapidly alternate (at a rate of 30 times per second) from full pressure to full release.

• Serpentine Belt and Tensioner - A poly v-belt, which wraps around several pulleys and idlers.  The tensioner keeps the serpentine belt tight against the pulleys and maintains proper tension at all times.
• Fan Clutch Assembly - A viscous (fluid) drive-coupling device connected to the center of the fan to permit variable engine fan speeds in relation to engine speeds.  The clutch engages and disengages the fan according to the engine temperature through a thermostat.
• Flush - To cleanse a system by sending water or other liquid through a system.
• Radiator - A device that cools the liquid in the cooling system by allowing it to circulate through a series of water channels, which are exposed to air ducts.
• Radiator Hoses - The rubber pipe connecting the radiator to the cylinder block.
• Heater Hoses - A flexible tube used to convey liquid.
• Blower Motor and Controls - A fan for an interior heating and ventilating system or even for an air-cooled engine.
• Thermostat - A temperature sensitive device used in the cooling system between the cylinder block and radiator.  It is set into the engine block and shuts off the circulation of water until the temperature of the water reaches the point at which the thermostat is set to open.  The thermostat cycles on and off and can fail if it is stuck open (vehicle runs too cold) or stuck shut (vehicle runs too hot).  Because automotive internal combustion engines operate more efficiently when their temperature is maintained within narrow limits, the thermostat closes off the flow of coolant from the engine to the radiator until the engine has reached the desired operating temperature.
• Electric Cooling Fan - A fan is a rotating device with curved blades like a propeller.  The primary fan in a vehicle is located behind the radiator.  Some electric fans may be placed in front of the radiator.  It draws air through the radiator so that the coolant looses its heat through the fins of the radiator.  It is especially needed when the vehicle is idling or moving slowly.  In some cases, the fan is automatically disengaged.
• Coolant - Liquid in the cooling system.  Usually a mixture of water and antifreeze (ethylene glycol).  This mixture lowers the freezing point and raises the boiling point of the water in the cooling system, prevents rust and corrosion, lubricates the water pump, and picks up heat from the engine and transfers it to the air passing through the radiator.  A proper mix of coolant is important for good protection.

• Ball Joints - A flexible joint using a ball and socket type of construction, used in steering linkage setups, steering knuckle pivot supports, etc.  Their flexibility helps to compensate for the changes in the wheel and steering when turning or hitting a bump on the road.  There are usually upper and lower ball joints attached to the upper and lower A-arms.
• Control Arms - A metal strut on the suspension, which is located at the top and bottom of the wheel spindle.  The upper and lower control arms allow the front wheels to change direction.  Also called a "wishbone" or "A-arm."
• Shocks - Properly called a damper, this is an oil filled device used to control spring oscillation in the suspension system.  At least one shock absorber is found at each wheel.
• Struts - A single, self-contained pivoting suspension unit that integrates a coil spring with a shock absorber.  Struts are used on front wheel drive automobiles.
• Sway Bar - Sometimes called the "anti-sway bar," "stabilizer bar," or even (incorrectly) "roll-bar."  It is usually a round bar, which connects the left wheel suspension assembly with the right side.  It may be found at the front and/or rear.  Its main function is to keep both wheels rolling at the same rate when meeting bumps; but it also affects handling.
• Wheel Bearings and Seals - The bearings in wheel hubs: ball bearings for drive shafts and taper roller bearings for driven hubs.
• Idler Arms - In a parallel relay-type steering linkage, it is one of the connecting levers.  The steering gearbox is attached to a pitman arm, which converts rotary motion to lateral motion. The pitman arm connects to a transverse centerlink, which connects to the idler arm attached to the frame side rail on the opposite side of the vehicle.  The ends of the centerlink connect to two adjustable tie rods that transmit the lateral movement of the centerlink to the steering arms at each steering knuckle.
• Pitman Arm - A short lever arm splined to the steering gear cross shaft, the pitman arm transmits the steering force from the cross shaft to the steering linkage system. In this way rotary motion of the steering wheel is turned to lateral movement of the arm.
• Tie Rod Ends (Inner and Outer) - A type of ball joint, which transfers the movements of the steering wheel to the wheels. Grease fittings or ball joints located on the ends of the steering linkage.
• Front End Alignment - The adjustment of the camber and caster of the front wheels. It is important for proper handling and long tire life.
• Springs - A device on the suspension system to cushion and absorb shocks and bumps and to keep the vehicle level on turns. After the stress or pressure exerted by the flexing of the spring has been removed, the spring returns to its original state. The spring does this by first absorbing and then releasing a certain amount of energy. The form of spring may be leaf springs, coil springs, torsion bars, or a combination of these.

• Rack and Pinion - A type of steering system with a pinion gear on the end of the steering shaft. The pinion engages a long rack (a bar with a row of teeth cut along one edge). When the steering wheel is turned, the pinion turns and moves the rack to the left or right. This movement is carried through tie rods to the steering arms at the wheels.
• Power Steering Pump and Hoses - A pump, which supplies hydraulic pressure for the power steering system.

• Cylinder Heads - The detachable metal (aluminum or iron) plate or cap that is bolted to the top of the cylinder block. It is used to cover the tops of the cylinders, in many cases the cylinder head contains the valves, it also forms part of the combustion chamber. It has water and oil passages for cooling and lubrication. It also holds the spark plugs. On most engines a valve cover or rocker arm cover is located on top of the cylinder head. Some engines have just one cylinder head covering several cylinders, while others have separate heads for each cylinder.
• Valve Cover Gaskets - A gasket between the cylinder head and the valve cover; usually either a flat paper or cork gasket or an O-ring.
• Engine Mounts - A flexible support for the engine in which an elastic medium, usually rubber, is interposed between the lugs on the engine and the frame of the vehicle. They are used to reduce engine vibration to the passenger compartment.
• Pistons and Rings - A metal, split ring installed in the groove on the outside wall of the piston. The ring contacts the sides of the ring groove and also rubs against the cylinder wall thus sealing the space between the piston and the wall. Poor rings can cause poor compression and severe blowby, often seen as blue smoke out the exhaust pipe.
• Timing Belt - A toothed belt driven by the crankshaft and operates the camshaft. It causes the valves to open and close at the proper time. When an engine is rebuilt, it is important to line up the crankshaft sprocket camshaft sprocket before applying the belt. When the belt breaks, often a valve will remain open and be hit by the rising piston causing the valve to bend and other internal damage.
• Timing Chain - A drive chain driven by the crankshaft and operates the camshaft. It causes the valves to open and close at the proper time. In OHC engines, it is called a cam chain.
• Oil Pan - The removable metal chamber or bowl (usually of sheet steel or cast alloy) at the bottom of the crankcase into which the oil drains to be stored. The oil drain plug is found at the bottom of this pan and can be removed to allow the old oil to flow out of the vehicle during an oil change.
• Front and Rear Bearing Seals - It is used to keep grease and oil from leaking out and protects bearings from dirt and water.
• Oil Cooler Lines - These lines are used to cool off the engine oil or the automatic transmission fluid.

• U-Joints - A flexible double-pivoted joint that allows driving power to be carried through two shafts that are at an angle to each other. It consists of two Y-shaped yokes and a cross-shaped member called the spider. The four arms of the spider are assembled into bearings in the ends of the two yokes. With the normal cross-and-two-yoke universal joint there is some change in speed when the driveshaft and the driven shaft are at an angle to each other. The change in speed occurs because the driven yoke and driven shaft speed up and then slow down twice with every revolution of the driveline. The greater the angle between the drive and driven shafts, the greater the speed variation. To eliminate this speed variation, which results in increased wear of the affected parts, constant velocity joints are used on many cars. In front drive vehicles; it is called the constant velocity joint.
• CV Joints (Constant Velocity Joints) - A type of universal joint so designed as to create a smooth transfer of torque from the driven shaft to the driving shaft without any fluctuations in the speed of the driven shaft.

• Control Arms - A metal strut on the suspension, which is located at the top and bottom of the wheel spindle.
• Rear Shocks - Properly called a damper, this is an oil filled device used to control spring oscillation in the suspension system. At least one shock absorber is found at each wheel.
• Height Sensor - A suspension system using air rather than metal springs to support the vehicle and control ride motions. Air spring results in a smoother ride, because the natural frequency of vibration of an air spring does not vary with loading as it does with metal springs. Air springs can be made very soft for the lightly loaded condition and the pressure automatically increased to match any increase in load, thus maintaining a constant spring rate for any load.

• Axles and Seals - It is used to keep grease and oil from leaking out and protects bearings from dirt and water.
• Differentials - A unit that takes the power of the rotating driveshaft at right angles to the rear axle and passes it to the axle. It will not only drive both rear axles at the same time, but will also allow them to turn at different speeds when negotiating turns. In this way the tires do not scuff or skid.
• Pinion Shaft - A short drive shaft in the rear axle connecting the prop shaft to the ring gear via the final drive pinion.
• Transfer Case - An auxiliary device in a 4-wheel-drive vehicle that allows power to be delivered to both axles. Normally the transfer case incorporates a shifting device so that the front drive can be disconnected, if desired, for running on pavement. On most new vehicles, 4WD is on all the time, and is controlled by a 4WD module. Tire size is very important when owning a 4WD vehicle. Tire wear or different diameter tires can cause premature breakdown of the transfer case.

• Accumulator - A storage tank, which receives liquid refrigerant from evaporator and prevents it from flowing into the suction line before vaporizing.
• Clutch and Pulley - A clutch part on an air condition compressor, consisting of hundreds of windings of wire, that creates a magnetic field when current is applied, pulling in the drive plate to engage the clutch.
• Compressor - A mechanism in an air conditioning system that pumps vaporized refrigerant out of the evaporator, compresses it to a relatively high pressure and then delivers it to the condenser.
• Condenser - The unit in an air conditioning system that cools the hot compressed refrigerant and turns it from a vapor into a liquid. It is the opposite of an evaporator.
• Evaporator - The unit in an air conditioning system used to transform refrigerant from a liquid to a gas. It is at this point that cooling takes place as heat is removed from the air.
• Freon - A gas used as the cooling medium in older air conditioning and refrigeration systems. Usually called freon-12 or R-12. It has been replaced in automobiles with a new refrigerant designated 134A.

• Clutch - A spinning plate located at the end of the driveshaft facing the engine flywheel and covered with a friction material such as asbestos. When the clutch is engaged, the disc is squeezed between the flywheel and the clutch pressure plate, causing the engine and the transmission to turn at the same speed, thus transferring power from the engine to the transmission.
• Speedometer - Instrument usually found on the dashboard, which is used to determine forward speed of a vehicle in kilometers per hour or miles per hour.
• Mounts - Used to attach the transmission to a support. They are made of rubber.
• Transmission Pan - Metal or cast aluminum cover that allows access to some transmission components; for example the transmission filter. A common point for leaks to occur is the transmission pan gasket.
• Transmission Lines - Transmission fluid needs to be cooled. This is accomplished by a cooler in the front of the vehicle, usually the radiator. Can be steel or rubber. A common point for leaks to occur.
• Valve Body - Part of the valve assembly containing plungers, pistons, springs, etc.
• Front Pump - Located in the front of the transmission behind the torque converter. The transmission pump is the "heart" of the transmission. The seal between the torque converter and pump is a potential source for leaks.
• VSS - The sensor in speedometer cluster, which sends the vehicle speed information (i.e., how fast the car is traveling) to the electronic control module.
• Neutral Safety Switch - A switch, which allows the starter to be engaged only when the automatic shift lever is in either park or neutral.
• Torque Converter - A unit in an automatic transmission that transfers engine torque to the transmission input shaft. It also cushions the flow of power.
• Modulator - A pressure control or adjusting valve used in the hydraulic system (i.e., hydraulic modulator) of the automatic transmission. When the vehicle is under heavy load or full throttle, the modulator increases the pressure to hold the clutches in place. In a light load situation, the modulator reduces pressure to give smoother shifts.
• Shift Linkage - The rods, levers, etc. used to transmit motion of the shift lever into movement of the gears in a gearbox.
• Trans Service and Flush - To cleanse a system by sending water or other liquid through a system.
• Slave Cylinder - A small cylinder containing a piston which, under hydraulic pressure from a master cylinder, operates the brake shoes or pads in hydraulic brakes or the working part in any other hydraulically operated system (such as a clutch slave cylinder).

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