Exhaust Gas RECIRCULATION: Description

Exhaust Gas Recirculation (EGR) System used on General Motors vehicles is designed to reduce emission of oxides of nitrogen (NOx). This is accomplished by lowering combustion temperatures of burning gases. Recirculated, metered amounts of exhaust gases are reintroduced into engine through intake manifold where they are mixed with air/fuel mixture. System consists of an EGR valve, a thermal vacuum switch and a modified intake manifold. Some vehicles are equipped with a dual diaphragm EGR valve for more precise control under varying engine loads.