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Parts Glossary |
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Glossary of Automotive Components/Terms
CV stands for Constant Velocity. These joints are mostly found on front wheel drive, 4 wheel drive, or rear engine cars, but can be found on some luxury rear wheel drive cars. They allow a driveshaft to propel the wheel smoothly at the sharp angles caused by front wheels being turned right and left, and up and down suspension movements. CV joints are similar to a universal joint (U-joint) except they will compensate for much higher angles.
CV Boot. A rubber accordion cone shaped boot that goes around a CV axle joint. The boot holds in lubricant to keep the joint from overheating and keeps dirt and moisture out of the bearings.
CV Joint without boot.
Coolant Temperature Sensor/CTS/ECT
Measures the temperature in the cooling system, so the ECM can
make adjustments based on the engine's operating temperature.
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Crankshaft or Camshaft Position Sensor/CPS
Monitors the rotation and position of the engine and tells the
computer exactly when to trigger the fuel injectors or the ignition spark.
EGR stands for Exhaust Gas Recirculation. The EGR system recirculates a small portion of exhaust back into the engine cylinders to cool the combustion process during light to medium engine loads.
The EGR valve was introduced in the early 1970’s as a
quick fix to reduce a nasty emission called Nitrous Oxides. At first
performance could sometimes be improved by disconnecting the valve (a legal
no-no) but after the engineers had time to incorporate them into the system,
they discovered that they could use the EGR process to allow higher timing
advances and compression, thereby improving
performance and mileage.
If your EGR valve doesn’t function correctly it will cause engine pinging and effect mileage to some degree. In some cases it can even cause engine damage if it’s not working. The EGR system shouldn't function at idle or full throttle. Operation at idle will cause rough idle and/or stalling.
A sensor mounted in the engine block that senses the type of
vibrations given off by cylinder detonation (pinging). When the on-board
computer sees signals from this sensor indicating detonation or pinging it retards
ignition timing to try and eliminate the problem.
Reads changes in barometric (air) pressure. The ECM uses this
information to adjust timing advance and air/fuel ratio.
Mass Air Flow Sensor/MAF Sensor
Measures the amount of air drawn through the engine's air
intake, so the computer can calculate amount of fuel to inject and compensate for
engine load, altitude and temperature.
A sensor in the exhaust system that measures oxygen content and is used by
the on-board computer to adjust fuel mixture. To be efficient this sensor
needs to send signals to the computer many times every second . This sensor
doesn't start operating until it reaches 600 degrees F. and needs to be
between 800 and 1200 degrees to be accurate.
PCV Valve/Positive Crankcase Ventilation Valve
Removes partially-burned gases and moisture from the crankcase improve
economy and reduce emissions while preventing buildup of sludge and corrosion
in the engine.
Monitors the position of the accelerator pedal and the throttle linkage, so
the ECM can make accurate air/fuel mixture adjustments.
Controls spark timing, fuel delivery and emission controls. In some
vehicles it also controls transmission, cooling fans, cruise control, climate
control, speedometer and many other accessories. It continuously
receives signals from sensors and input devices and sends
control signals to valves, controllers and other output devices. Stores
"trouble codes" and warns driver when service is needed.
Engine thermostats are a big cause of poor gas mileage and poor engine performance.
A thermostat is a valve located in the engine that prevents the engine coolant from circulating through the radiator until the engine temperature reaches a predetermined temperature, about 190 -
195 degrees Fahrenheit on most cars. After this temperature is reached the thermostat attempts to keep the coolant flow to the radiator regulated to maintain proper temperature,
about 190 - 220. A tired thermostat
that won't maintain proper temperatures can cause many problems, such as poor mileage, pinging, hesitation and surging as well as engine
damage and oil sludging.
Although they often stick closed and cause overheating, the most common failure is opening too soon or sticking open and causing the engine to run too cool.
This can start happening after only two years, so our recommendation is to replace them every 2 - 3 years.
When purchasing one, make sure you ask for the manufacture's recommended
temperature, usually around 195 degrees. We've found a lot of people using the wrong temperature because of a recommendation from someone at a parts counter or a "friend".
