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Home >> Audi >> 1991 >> 100 Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Idle Control System 2.2L >> Idle Speed Stabilization System
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Idle Speed Stabilization System

  1. Ensure engine temperature is less than 68°F (20°C). Disconnect harness connector at thermoswitch. Check continuity of idle stabilizer thermoswitch to ground.
  2. If continuity does not exist, replace idle stabilizer thermoswitch. If continuity exists, warm idle stabilizer thermoswitch to at least 104°F (40°C). Thermoswitch should now show an open circuit. If not, replace idle stabilizer thermoswitch.
  3. Warm engine to at least 176°F (80°C). Disconnect electrical harness for idle stabilizer valve. Connect a voltmeter across both terminals. Turn ignition on. Ensure battery voltage is present. If battery voltage is not present, go to step 5).
  4. If battery voltage is present, reconnect idle stabilizer valve. Touch idle stabilizer valve to check for vibrations. If vibration is not felt, replace idle stabilizer valve.
  5. Remove idle stabilizer control unit (located in relay panel). Turn ignition on and ensure battery voltage exists between terminals No. 14 (socket 11) and No. 5 (socket 12).
  6. If battery voltage does not exist, repair wiring. Turn A/C on. Ensure battery voltage exists between terminals No. 2 (socket 12) and No. 5 (socket 12). If battery voltage is not present, check wiring from A/C relay pin No. 87M in relay panel.
  7. Check resistance between terminals No. 4 (socket 12) and No. 11 (socket 11) of idle stabilizer control unit. Ohmmeter should indicate 20-40 ohms. If resistance is not 20-40 ohms, check continuity of wiring between idle stabilizer valve and relay board.
  8. Ensure throttle switch is at idle position. Ensure battery voltage exists at terminal No. 8 (Gray wire) of idle stabilizer control unit. If battery voltage does not exist, check and adjust throttle switch or repair wiring. When battery voltage is present at idle, open throttle slightly. Ensure voltage drops to zero.
  9. Disconnect idle stabilizer thermoswitch harness lead. Ensure continuity exists between terminal No. 13 (socket 11) and thermoswitch lead (Blue/Green wire). If continuity does not exist, repair wiring. If all circuits of idle stabilizer system are okay and idle stabilizer valve still does not work, replace idle stabilizer control unit.
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