Glossary of Automotive Components/Terms

EGR Valve

EGR stands for Exhaust Gas Recirculation. The EGR system re-circulates 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 improvingEGR valve performance and mileage.

If your EGR valve doesn't function correctly it can cause engine pinging or detonation and will effect mileage to some degree. In some cases it can even cause engine damage if it is not working. The EGR system shouldn't function at idle or full throttle. Operation at idle will cause rough idle and/or stalling.

Many times if the computer sees a problem with the EGR system it will reduce ignition timing advance which causes loss of fuel mileage. 
























 

 

 

 

 

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