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Discussion Starter · #1 ·
I just recently put on a new IAC and had a crazy high idle. So I adjusted it, but now it is idling too low in the cold. This may be a dumb question because I forgot when I adjusted it, but which way do I need to rotate the plunger to raise the idle rpm's?
 

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I just recently put on a new IAC and had a crazy high idle. So I adjusted it, but now it is idling too low in the cold. This may be a dumb question because I forgot when I adjusted it, but which way do I need to rotate the plunger to raise the idle rpm's?
I don't know what you mean by adjusting the IAC. It works of the vehicles Computer. If your trying to pull or push on the plunger there'e a chance you may have damaged it. When a new IAC is installed the ECM has to learn and adjust the IAC.
 

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The IAC is not user adjustable. The computer sets/adjusts it to get the rpms it wants.
 

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Sounds like the stepper motor or the PCM or the harness has an issue and the IAC just stays at whatever plunger length he installs it with

Last guy that had a similar issue turned out to be a bad PCM verified with cross checking pin to pin on PCM resistance with harness unplugged

I was doubtful it was PCM until we compared resistances and in the end it all worked with a new PCM
 

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Discussion Starter · #6 ·
Well when I first installed it the rpm's would sit at like 2000 rpm's. I read that it would self adjust. So I gave it a few days. It didn't so I took the IAC off and adjusted the plunger and the rpm's then settled around the 700 range at idle. In the cold though it would be closer to the 500 mark and would die if I wouldn't let it warm up. So I was able to adjust the plunger to match the length of the original IAC.

So maybe that isn't what I need to adjust for my idle rpm's then. Do you guys think my pcm might be bad?
 

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Well when I first installed it the rpm's would sit at like 2000 rpm's. I read that it would self adjust. So I gave it a few days. It didn't so I took the IAC off and adjusted the plunger and the rpm's then settled around the 700 range at idle. In the cold though it would be closer to the 500 mark and would die if I wouldn't let it warm up. So I was able to adjust the plunger to match the length of the original IAC.

So maybe that isn't what I need to adjust for my idle rpm's then. Do you guys think my pcm might be bad?
The plunger is moved in and out by the controller so all you did was move it to a different position while it was static. After you started the engine the computer took over again. It sounds like there was an initial vacuum leak when you first installed the controller which you accidentally corrected when you removed it again.

You may want to disconnect the battery to reset the computer for starters. Also what brand IAC did you install and did you thoroughly clean the TB before installing the new part.
 

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Sounds like the PCM is no longer moving the stepper motor that moves the plunger in and out as if it could move it his removal and hand adjust of plunger would have done nothing as the stepper again took over after engine was started

Bad IAC stepper or harness or PCM not just a vacuum leak
 

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Discussion Starter · #11 ·
Perfect. Thank you. It looks like the other guy did a lot of the same things I have already done. I may need to get a new IAC because I manually adjusted it, and a pcm.
 
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