Corolla, Pickup & Tercel Federal

Inspect HAC valve. Visually inspect and clean air filter in bottom of HAC valve.
On Corolla, disconnect electrical connector from Electronic Bleed Air Control Valve (EBCV). On all models, at altitudes greater than 3930 feet and with engine idling, blow into any of the 3 ports on HAC valve. Check that air escapes from bottom of HAC valve.
If HAC valve does not function as described, replace valve. See Fig 1, Figure or Figure. If HAC valve is okay, go to step 6). On Tercel, inspect individual components. Test check valve and restrictor.
On Corolla, unplug electrical connector from Electronic Bleed Air Control Valve (EBCV). On all models, at altitudes less than 2750 feet, with engine idling, unplug electrical connector from valve. Blow air into any of the 3 ports on HAC valve. Check that air does not escape from bottom of HAC valve.
If HAC valve does not function as described, replace valve. See Fig 1, Figure, or 69. On models except Tercel, if HAC valve is functioning properly, go to next step. On Tercel, inspect individual components. Test check valve and restrictor.
On Corolla & Pickup, check ignition timing. Disconnect vacuum hose from distributor sub-diaphragm (outer hose) and plug hose end. Note base timing. Reconnect hose to distributor.
On Corolla, timing should advance to approximately 13 degrees BTDC at 900 RPM. On Pickup, timing should advance to 12 degrees BTDC at 950 RPM.
If HAC system does not function as described, test check valve and distributor vacuum advance unit.

Fig 1: Corolla HAC System Components & Operating Parameters

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Fig 2: Pickup HAC System Comp & Operating Parameters

Fig 3: Tercel HAC System Components & Operating Parameters