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 MANUALSAUDI199590 BASE, 2.8 K, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - SYSTEM/COMPONENT TESTSIDLE CONTROL SYSTEMIDLE AIR CONTROL (IAC) VALVE
1995 Audi 90 Base, 2.8 K, Automatic
Idle Air Control (IAC) Valve
1995 Audi 90 Base, 2.8 K, AutomaticSECTION Idle Air Control (IAC) Valve
- Disconnect electrical connector from Idle Air Control (IAC) valve. See ELECTRICAL COMPONENT LOCATIONS . Measure resistance between IAC valve connector terminals. If resistance is not 7-11 ohms, replace IAC valve. If resistance is 7-11 ohms, remove IAC valve.
- Looking through hole in IAC valve, check for scored rotary slide valve. Replace IAC valve if rotary slide valve is scored. If rotary slide valve is okay, reconnect IAC valve connector. Turn ignition on. Initiate Output DTM. See OUTPUT DIAGNOSTIC TEST MODE (DTM) under SELF-DIAGNOSTIC TESTS in TESTS W/CODES article. Observe rotary slide valve when IAC valve is activated during Output DTM.
- If rotary slide valve travels freely from stop to stop, system is okay. If rotary slide valve shows signs of movement but does not travel freely from stop to stop, replace IAC valve. If rotary slide valve is not activated during Output DTM, check wiring. If wiring is okay, replace PCM.
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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.