Idle Air Control(IAC) Testing Replacing -Cleaning for 99+

01-16-2007, 09:25 PM
This is for the 99+ Grand Ams.

Testing & Replacing is for the 2.4L, 3.1L, & 3.4L.

The IAC regulates the air by passing the Throtle body(TB) by moving its pintal in and out of the passage way.
If this is even partially pluged it can effect Idle.

The IAC is controled by the PCM, adjusting idle speed depending on running conditions ,
AC, powersteering, cold or warm. Other wise Idle is not adjustable.

Working action looks something like this at idle;

The IAC is on the right side of the Throtle Body(TB).
Should be facing forward of car on the 4cyl.

*4 Cyl Location pictured here (
*V6 Location Picture here (

Testiing the IAC

- With the engines cold the IAC should increase the idle and vary as it warms up.
- With the engine warmed up and place a load on the engine by turning on hte AC or turn the steering wheel.
- The idle should remain steady or increase a little.
- If it stalls or stubles then the IAC is not working proprly.

- Shut the engine off, disconnect the electrical connector from the iAC.
- The terminals are # left to right.

- Using an Ohm metter test the resistance acrossed terminals 1-2, then measure acrossed 3-4.
- The readings should be about the same on both sides.
- If one of them shows an open circuit replace the IAC.

- If the IAC checks ok, it could be your PCM which a dealer will have to check.

-- Replacing the IAC--
Warning - DO NOT push or turn the pointy tip of the IAC.
This will mess up the calibration.

- Disconnect the negative battery terminal.
- Remove the air intake tube is needed to gain access to the IAC, like on the 2.4L.
- Disconnect the plug in on the IAC.
- Remove the 2 torx screws.
- Remove the old "O" ring.

** If installing a new idle air control valve it'll need adjusted.
- Measure the distance of the valve plunger that is extended.
**Measurement should be made from the edge of the valves mounting flange, to the end of the cone.

- The distance should not exceed 1-1/8 in. (28mm),
or damage to the valve may occur when installed.

-If the measuring distance is greater than specified above,
use your finger pressure to slowly retract the pintle,
by using a slight side to side motion to help it retract it easier (valve with collar at electric terminal end),
or compress the retaining spring from the valve while turning the valve "in" with a clockwise motion.

- Return the spring to its original position with the straight part of the spring end aligned with the flat surface of the valve (valve without collar at electric terminal end).

-Use a new gasket "O" ring, then position the idle air control valve in its mounting position.
-Install in reverse prcedurre.

Hope this helps!

04-22-2008, 07:29 PM
IF you are having troubles with idling, or cold starts, try cleaning the IAC

Make sure the spring on the IAC is clean , clean the passage into the intake, and also the end tip(pintle) should be clean around the surfaces. Spraying TB cleaner into the port/opening should remove any excess carbon build up. Might try letting it soak for a few.

Red arrows indicate where it should be cleaned, and is in good shape, and is clean.
yello arrow is the "O" ring.

Also make sure the IAC is dry before pluging it in to the wire connector.

Here is a pic of the IAC port, you can see small amounts of carbon still deep inside. Use A Q tip and TB cleaner to clean it out very good.

This is the back side of the TB's IAC port, it needs cleaned along with the TB butterfly..

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