The EGR Valve is the “exhaust gas recirculation” valve. It is part of the car’s circulation system and helps control the level of pollution (or car exhaust) while maintaining the car’s over-all efficiency. Car pollution has been an important concern since the 1960’s but has received greater attention today because of growing environmental awareness.
If an EGR valve is broken car users will hear a knocking sound or what some people call “rough idling.” This is one sign that the valve has become clogged or in some way is not working up to maximum efficiency.
An EGR valve helps reduce pollution by sending some of the exhaust back into the combustion chamber. This lowers the chamber’s temperature. This lowers the production of nitrogen oxides, which is one of the main causes behind smog.
EGR valves have a relatively simple construction, opening and shutting in order to control the amount of exhaust that re-enters the chamber. However, these require a certain level of back pressure so that the valve won’t remain open when the engine is left to idle (during these situations, the combustion chamber needs more oxygen). If the valve is stuck open, the car combustion can become inefficient. The car can stall because of lack of atmospheric oxygen. If the car is stuck closed, the nitrogen oxide levels may become so high that the car “knocks” or ignites little sparks which cause problems in the timing of the engine.
Mechanical valves that have become clogged can become clean. However, any problems with electronic valves may require replacement.