General Description

The Exhaust Gas Recirculation (EGR) system is designed to:
^ reintroduce exhaust gas into the combustion cycle.
^ lower combustion temperatures.
^ reduce the formation of nitrous oxide.

The amount of exhaust gas reintroduced and the timing of the cycle varies by calibration. Timing and volume are controlled by the following:
^ engine rpm
^ engine vacuum
^ exhaust system back pressure
^ engine coolant temperature
^ throttle position

The EGR valve is vacuum actuated.

The differential pressure feedback EGR system:
^ monitors EGR flow rate by the pressure drop across the metering orifice.
^ uses an EGR pressure transducer as the feedback device.
^ controls pressure that is varied by the valve movement using vacuum output of the EGR vacuum regulator solenoid.
^ uses the EGR valve only as a pressure regulator, rather than a flow metering device.
^ allows for a more accurate assessment of EGR flow requirements.