Random high idle

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YoshiNote
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Joined: Fri Aug 10, 2018 11:48 pm

Random high idle

Postby YoshiNote » Sat Sep 08, 2018 9:40 pm

95 Chevy Beretta 3.1 random idle on start I've tried replacing the idle control the TPS and the mass air flow I can hook it up to tune Pro it shows Everything Green any ideas of what else it could be it's random sometimes it's normal idle sometimes it's high idle it does have an aftermarket air intake also took the throttle body off completely cleaned it put new gasket on and cleaned the little chamber that leads to the EGR valve and put a new gasket on the EGR valve I can't seem to find any vacuum leaks any ideas would be helpful



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GT_Indy
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Re: Random high idle

Postby GT_Indy » Mon Sep 10, 2018 10:06 am

I don't know if this is what you are having, but on my 96 with the 3100 I kept getting high idle and low idle problems at one point, I was doing the same thing, checking for vacuum leaks, checking my sensors, replacing the IAC, made sure the throttle body was clean, checked MAF and fuel etc.
Turns out several new IAC valves were faulty from the store, I went through about 4 new ones before I finally got a working part then the car ran perfectly fine again.
This was about 2 years ago for me.

I did the same thing, I was checking my scanner and all my sensors looked perfectly fine. The IAC does not give feedback to the computer, so everything can look good but if the IAC has a dead spot and it is causing high idle, the computer won't know. A bad IAC acts like a vacuum leak or a plug depending where it is set when it fails.

I suggest getting a known good IAC valve and swapping it onto the car.
Another thing to remember is the IAC valve can break easily if you pull or push on the center piece by hand when it is out of the car.

Also it is good to verify the TPS is installed correctly and not holding the throttle open a little bit. But that should not be a problem.


96 Beretta Z26 swap
90 Beretta GTZ
90 Beretta Indy


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