i went to drop my roommate off at the car shop next to a test only smog station...i told him my car failed the NO part of smog...and he said that i should check the egr valves...can anyone tell me wat this is where, and wat it does....thanks

 

egr stands for exhaust gas recirculation. The egr valve allows some very inert gas to get back into the combustion chamber only when needed. it allows some of the exhaust gas to get back into the intake manifold under strict control and only when we need it. That would cool the combustion chamber and prevent the formation of the NoX. to tell if your egr valve is not working...it can be open when it isn't supposed to be, or it can be closed when it is supposed to be open. Not rocket science, but it is science. If it is open when it is not supposed to be open, at idle for instance, It will act like one monster vacuum leak and the engine will not idle or will idle really roughly. If it doesn't open when it is supposed to open you will probably experience a symptom of "pinging" or "knocking" since the combustion chamber temperature will be higher than normal (one of the main causes of pinging in an engine). hope this helped