Exhaust Gas RECIRCULATION: Description

Exhaust Gas Recirculation (EGR) is used on all Light Duty emissions models to reduce oxides of nitrogen (NOx) emissions. This process is accomplished by lowering the combustion temperatures of burning gases. Recirculated metered amounts of exhaust gases introduced into the intake manifold dilutes the air/fuel mixture and lowers combustion temperature.

EGR valves used on all 1975-76, and 1977-78 Federal models are either single or dual diaphragm type. 1977-78 California and High Altitude models, and all 1979 models use a single diaphragm or backpressure modulated EGR system.

The backpressure modulated system regulates the timed vacuum according to the exhaust backpressure level. A special control valve within the EGR valve housing acts as a pressure regulator.