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Home >> Audi >> 1994 >> 90 CS Quattro >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Idle Control System >> Idle Air Control (IAC) Valve
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Idle Air Control (IAC) Valve

  1. Disconnect electrical connector from Idle Air Control (IAC) valve. See ELECTRICAL COMPONENT LOCATIONS  table at beginning of article. 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.
  2. 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 DTM in G - TESTS W/ CODES article in the ENGINE PERFORMANCE Section. Observe rotary slide valve when IAC valve is activated during Output DTM.
  3. 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 ECM.
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