Exhaust Gas Recirculation: Description and Operation

EGR Components:

Fig. 147 EGR Operation:

PURPOSE
The EGR System controls the formation of NOx (Oxides of Nitrogen) emissions by recirculating some of the exhaust gases into the combustion chamber. The exhaust gas in the combustion chamber lowers the peak ignition temperature.

OPERATION
The EGR valve is controlled by the ECM through the EGR solenoid and by exhaust back pressure acting on the Back-Pressure Transducer (BPT) Valve.

Vacuum is allowed to the EGR valve on acceleration and shut OFF upon deceleration or idling. The diaphragm mounted in the BPT valve raises in relation to exhaust pressure, opening an orifice allowing vacuum to be applied to the EGR Valve in response to the throttle opening.