IAC Help Needed
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Junior Member
Joined: Sep 2009
Posts: 23
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IAC Help Needed
Hi All, I could use your help.
I am trying to figure out how this IAC really works. I have a low RPM issue, especially when in drive.
With the engine running, 600 RPM, I backprobed the wiring harness. I am getting 2.8 volts. If I increase the idle to about 2500 RPM, it drops to 1.8 volts.
With the ignition ON, engine not running, harness disconnected, its around 12 volts.
Any idea on how many volts is required to activate the IAC? 2.8V seems low, but not sure.
With the IAC wiring connected or disconnected, the RPM is the same.
I did an ohm test and it is within spec.
Any thoughts on this?
I am trying to figure out how this IAC really works. I have a low RPM issue, especially when in drive.
With the engine running, 600 RPM, I backprobed the wiring harness. I am getting 2.8 volts. If I increase the idle to about 2500 RPM, it drops to 1.8 volts.
With the ignition ON, engine not running, harness disconnected, its around 12 volts.
Any idea on how many volts is required to activate the IAC? 2.8V seems low, but not sure.
With the IAC wiring connected or disconnected, the RPM is the same.
I did an ohm test and it is within spec.
Any thoughts on this?
Retired Aerospace
Joined: Dec 2008
Posts: 1,324
Likes: 14
From: Edgewater, Florida
Need a Scope:
The IAC is a variable air-bypass in parallel with the throttle plate. The signal driving the IAC is a +12-0 volt PWM (Pulse Width Modulation) from the PCM. The signal is a series of variable-width square-wave pulses that are averaged out at the IAC drive motor that controls the valve position and changes the bypass volume (the injectors work using the same principle). The 2.8 volt signal you see at idle is probably correct and the decreasing voltage as RPM rises is normal. At some point as the RPM increases the voltage will fall to zero and the valve will be closed.The squirrely idle might be caused by a dirty IAC or a messed-up bypass valve. Pull the thing apart and check the condition of the valve pintle and seat and see that the valve stem can be moved freely against the return spring, then give the whole thing a good scrubbing with carb cleaner..... Oh, and make sure the MAF sensor elements are clean.
Last edited by Kattumaram; Oct 28, 2009 at 05:34 PM.
Thread Starter
Junior Member
Joined: Sep 2009
Posts: 23
Likes: 0
Thank you for the response.
The condition occurs when the vehicle is at operating temperature.
I have cleaned the MAF.
The way I check the IAC voltage, I pin probe the back of the connector across the 2 wires. I assume this is correct?
Can I take apart the IAC? If so, how do I do this?
I have cleaned the IAC, but should probably check it again.
How freely should the pluger move? Also, how much should the plunger move? I believe it moves 1/8" when 12 volts are applied.
Thanks for your help and sorry for all the questions.
The condition occurs when the vehicle is at operating temperature.
I have cleaned the MAF.
The way I check the IAC voltage, I pin probe the back of the connector across the 2 wires. I assume this is correct?
Can I take apart the IAC? If so, how do I do this?
I have cleaned the IAC, but should probably check it again.
How freely should the pluger move? Also, how much should the plunger move? I believe it moves 1/8" when 12 volts are applied.
Thanks for your help and sorry for all the questions.