EGR System: Operation: Notes

EGR system on 2.2L carbureted engines uses ported vacuum to control EGR valve operation. The vacuum signal is further controlled by a Coolant Vacuum Switch (CVS), which prevents EGR operation until coolant reaches a predetermined temperature. The CVS is mounted on thermostat housing.

A backpressure type EGR system is used on 2.2L and 2.5L fuel-injected engines. The backpressure transducer measures the amount of exhaust backpressure and varies the strength of the vacuum signal to the EGR valve. The signal vacuum is bled off into the atmosphere when exhaust backpressure to the EGR drops below a calibrated value.

A backpressure type EGR system is used on 2.2L turbocharged engines. The logic module controls vacuum through the EGR solenoid, turning the vacuum circuit on or off. A backpressure transducer measures the amount of exhaust backpressure on the exhaust side of the EGR valve. The transducer varies vacuum signal strength to the EGR valve.

The logic module prevents EGR operation by turning the EGR solenoid off when engine temperature is less than 80°F (27°C) or temperature is more than 80°F (27°C) for less than 7 seconds. The backpressure transducer adjusts the EGR vacuum signal to provide programmed amounts of EGR under all other conditions.