Exhaust Gas Recirculation: Description and Operation

The EGR System controls the formation of NOx (oxides of nitrogen) emissions by recirculating some of the exhaust gases into the combustion chamber.

Fig. 21 EGR Components:

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.

When the ECU senses the predetermined conditions suitable for EGR operation, it de-energizes the EGR solenoid, redirecting vacuum from the source port and vent port to the source port and valve port allowing EGR operation.

Fig. 132 EGR Oeration:

^ Refer to the chart above for EGR system operating conditions.
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