GM Storm/Spectrum 1985-1993 Repair Guide

Idle Air Control Valve



See Figure 1

  1. Disconnect the negative battery cable.
  3. Remove the IAC valve attaching screws.
  5. Remove the valve from the throttle body.

To install:

Once an IAC valve has been in service, DO NOT push or pull on the pintle. The force required to move the pintle may damage threads on the worn drive.

  1. Carefully clean the IAC valve mounting surface to assure proper O-ring seal. The IAC valve is an electrical part, do not soak or immerse it in solvent.

When replacing the IAC valve, make sure only to use an identical part. The pintle shape and diameter are essential to proper valve operation and may vary from application to application.

  1. If installing a new IAC valve, measure the distance from the tip of the pintle to the flange mating surface. If the distance is greater than 28mm, retract the pintle using finger pressure. This will not harm a NEW IAC valve.
  3. Inspect the valve O-ring for damage, and replace, if necessary. Lubricate the O-ring with clean engine oil.
  5. Install the IAC valve to the throttle body.
  7. Install the IAC valve retaining screws and tighten to 27 inch lbs. (3 Nm).
  9. Connect the negative battery cable, then follow the Idle Learn Procedure.

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Fig. Fig. 1: Idle Air Control (IAC) Valve service


The ECM controls idle speed using the IAC valve by extending or retracting the valve pintle to control air flow. But to do this, the ECM must know at all times exactly where the pintle is located. If the battery cable is removed and power is lost, the pintle position will also be lost.

The ECM will normally reset the pintle position 1 time each ignition cycle, during moderate acceleration, once the vehicle speed passes 30-40 mph (depending on the model). The ECM accomplishes this by commanding the pintle to retract completely, then move inward to the fully seated position. This establishes a zero count, from which the ECM can back out the valve to its desired position.

If a problem occurs with the resetting, the ECM will repeat it until a proper count is established.

Any time power has been cut and the pintle position is lost, a drop in performance may be noticeable until the ECM has a chance to relearn proper positioning. To teach the ECM proper pintle position, the vehicle should be driven with the engine in normal closed loop operation (fully warmed) using moderate acceleration and speeds of at least 40 mph for 2-3 miles until normal performance returns.