EGR System: Operation

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

To control vacuum bleed off, an EGR leak orifice is used. This vacuum bleed off system is used on MPFI models and, also on Federal models with manual transmissions.

On all fuel injected models, EGR operating vacuum is controlled by a combination of 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.

Fig 1: EGR System (Federal Vehicles - M/T)

Courtesy of SUBARU OF AMERICA, INC.

Fig 2: EGR System (Single Port Fuel Injected Vehicles)

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Fig 3: EGR System (Federal Vehicles - A/T)

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Fig 4: EGR System (Turbo Vehicles)

Courtesy of SUBARU OF AMERICA, INC.