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Idle Air Control (IAC) valve relearn procedure

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iac relearn idle air control valve
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62 views 1 reply 1 participant last post by  sherlock9c1  
S
#1 · (Edited)
Is there an IAC relearn procedure for the Gen 2 LT1? Yes.

This applies to 1994-1995 LT1 engines run by the xxxx8051 PCM.
  1. Make sure the car is off.
  2. Press the gas pedal slightly.
  3. Start the engine.
  4. Release the gas pedal, run the engine for five seconds.
  5. Turn the ignition "OFF" for ten seconds.
  6. Restart the engine and check for proper idle operation.
Source: 1995 B-car Factory Service Manual (FSM), Volume 2, page 6E3-C2-17.
 
S
#2 ·
Additional notes from my own experience, and the GM FSM volume 2, page 6E3-C2-17:
  • IAC counts should be around 20-40 at hot idle on a stock LT1, as read by a scan tool, EEHack or 9495Scan.
    • If they are below this, and engine RPM is higher than normal, you likely have a vacuum leak.
    • If they are above this, the IAC passages may be clogged, or the throttle body may need cleaning.
  • If engine RPM does not respond to IAC commands from the PCM, the IAC may be dead. Use EEHack or a GM Tech2 scanner to command IAC position.
  • IAC resistance check with an ohmmeter:
    • should be between 40-80 ohms between terminals A-B and C-D.
    • should be infinite between A-D and B-C.
    • if any of these measurements are out of spec, replace the IAC.
  • Never move an IAC pintle once it has been used, or you may damage the internal threads.
    • If a NEW, never used IAC pintle is extended more than 28mm (as measured from IAC base to the end of the pintle tip), You may gently use finger pressure to slowly retract the pintle. It will not damage a NEW valve.
  • The IAC o-ring can be lubricated with clean motor oil during installation.
 
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