Although not essential, all modern gasoline automobile engines depend on exhaust gas recirculation or EGR valves to reduce toxic nitrogen oxides from emissions. The removal of EGR valves, while long debated, has not been shown to have any performance benefits.
Dangerous nitrogen oxide gases form when gasoline combustion chambers reach temperatures in excess of 2500 degrees Fahrenheit. To combat this, the EGR valve was introduced in 1973 by General Motors to recirculate exhaust gases into the combustion chamber, drastically reducing temperatures and the formation of nitrogen oxides. EGR valves do not function at idle or wide open throttle and generally increase fuel economy and performance.
For some, the benefit of more engine bay space is enough to make removing the EGR valve worthwhile. In order to do so without interferring with engine operation, the engine's electronic control module (ECM) must be set to never activate the missing EGR. Additionally, an EGR plate must be installed to cover the hole in the intake manifold where the EGR valve was installed.
On most cars a missing EGR valve will cause the vehicle to fail emissions testing because of a tripped check engine code and the presence of heightened levels of nitrogen oxides.
