Front Wheel Drive Models Exc. Calif. & High Altitude

Fig. 47 EGR system schematic. 1984-85 front wheel drive models w/V6-262/4.3L diesel engine, 3 spd. auto. trans. or 4 spd. manual trans. exc. Calif. & high altitude:

Fig. 48 EGR system schematic. 1984-85 front wheel drive models w/V6-262/4.3L diesel engine & 4 spd. auto. trans. exc. station wagon, Calif. & high altitude:

Fig. 49 EGR system schematic. 1984-85 front wheel drive station wagon w/V6-262/4.3L diesel engine & 4 spd. auto. trans. exc. Calif. & high altitude:

The basic EGR vacuum control system on these models operates in a manner similar to the system used on 1984-85 V8-350 engines, but the layout of components is varied, and some components have been added to further control EGR and TCC operation. All models use an injection pump mounted Vacuum Regulator Valve (VRV) to provide high vacuum at idle and progressively lower operating vacuum as throttle lever angle increases, a TCC cut-off solenoid to vent EGR vacuum when the converter clutch is engaged, and an Altitude Trim Solenoid (ATS) and Altitude Vacuum Regulator Valve (AVRV) to reduce EGR valve operating vacuum when the vehicle is operated above 4000 feet.
The system used on models with 3 speed automatic transmissions and 4 speed manual transmissions is the same as the 1984 V8-350 engine system, but the EGR-TVS is located between the AVRV and QRV, and the ATS and AVRV receive vacuum directly from the TCC solenoid, Fig. 47.
The system used on models with 4 speed automatic transmissions, except station wagons, includes a Transaxle Modulator Quick Response Valve (TM-QRV), Exhaust Pressure Regulator (EPR) valve, EPR Delay Valve (EPR-DV) and EPR-QVR, as well as all components used on other 1984-85 systems, Fig. 48. The EPR valve receives operating vacuum from the outlet port of the ATS, through the delay valve and QRV. At low altitudes, when the ATS is de-energized, the EPR valve receives the same vacuum signal as the EGR valve, after a 20-30 second delay caused by the inline delay valve. However, during high altitude operation when the ATS is energized, the EPR valve receives no vacuum as the signal is vented by the ATS. The EPR valve is fully closed when VRV vacuum exceeds 13 inches Hg, open when VRV vacuum is below 6.9 inches Hg, and serves to increase exhaust back pressure when closed or partially closed. The EPR-QRV and TM-QRV operate the same as the EGR-QRV, venting diaphragm chamber vacuum until it is constant with decreasing signal vacuum.
The system used on station wagon models with 4 speed automatic transmissions includes a Transaxle Modulator Vacuum Reducer Valve (TM-VRV) and Transaxle Modulator Quick Response Valve (TM-QRV) as well as all components used on 1984-85 V8-350 engines, and the EGR-TVS and TCC cut-off solenoid is located between the AVRV and EGR-QRV, Fig. 49. Vacuum is applied to the ATS, AVRV and TM-VRV directly from the injection pump mounted VRV. At low altitudes, when the ATS is not energized, vacuum is transmitted to both the EGR valve and transaxle modulator, and regulated by the VRV. However, at altitudes above 4000 feet when the ATS is energized, VRV vacuum is reduced 2.5 inches Hg to the EGR valve and 1 inch Hg to the modulator by their respective vacuum reducer valves.