EGR System: Operation

EGR valve receives operating vacuum from carburetor ported vacuum (throttle body ported vacuum for fuel injected models). A thermo vacuum valve, used on all carbureted models, bleeds off vacuum to EGR valve when intake manifold wall temperature is below 86°F (30°C). When intake manifold wall temperature reaches 104°F (40°C), vacuum bleed off stops and normal EGR operation begins.

To restrict vacuum bleed off, an EGR leak orifice, which is placed within bleed off line, is used. This vacuum bleed off system is used on all carbureted models except for auto. trans. equipped federal models.

On all fuel injected models, EGR operating vacuum is controlled by the ECU and the EGR solenoid valve. This system does not allow EGR operation until engine reaches normal operating temperature or at wide open throttle. On turbo equipped models, EGR operation is cancelled during turbo boost conditions.

Fig 1: Exhaust Gas Recirculation System (2WD Federal Models & Federal Models with Manual Transmission & All Calif. Models)

Fig 2: Turbo Exhaust Gas Recirculation System (4WD Federal Models with Automatic Transmission)

Fig 3: Exhaust Gas Recirculation System (2WD Federal Models with Automatic Transmission)

Fig 4: Exhaust Gas Recirculation System (4WD Federal Models with Automatic Transmission)

Fig 5: Exhaust Gas Recirculation System (Non-Turbo Fuel Injected Models

Fig 6: Exhaust Gas Recirculation System (Turbo Equipped Fuel Injected Models)