Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSUBARU1989XT 1.8 4, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMSYSTEM/COMPONENT TESTSIDLE CONTROL SYSTEMAUXILIARY AIR VALVE (MPFI 1.8L)
1989 Subaru XT 1.8 4, Automatic
Auxiliary Air Valve (MPFI 1.8L)
1989 Subaru XT 1.8 4, AutomaticSECTION Auxiliary Air Valve (MPFI 1.8L)
- With engine running, pinch hose between Auxiliary Air Valve (AAV) and intake manifold. Engine speed should drop (about 100 RPM with engine warm, more with engine cold). Release hose. Ensure engine speed returns to previous speed.
- If not as specified, turn ignition off. Ensure resistance of AAV is between Zero and Infinity ohms. If not, replace AAV. Check AAV solenoid for any short to ground. If present, replace ACV.
- Check for voltage at harness connector. Ensure 12 volts are available at Blue wire of AAV electrical connector. If not, check main relay, fuses and power source.
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.