high rev on start up - Ford Mustang Forum
 
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post #1 of 4 (permalink) Old 07-06-2006 Thread Starter
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Angry high rev on start up

'86 mustang conv. Love my car, only a few problems. High rev on start up. Stays around 1200 rpm's then goes to about 900 and stays there. When I pull of the IAC valve the car smooths right out. When I plug it back in, it goes to the high idle. I have replaced the IAC and cleaned out my intake. I also changed the TPS and still nothing. Thinking of changing the throttle plate. Is there anyway to adjust the idle on the 5.0 HO with the MPI? I'm really not a ditzy chick, I work in auto parts store and have quit a bit of basic car knowledge, but this is driving me crazy. Can you help???
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post #2 of 4 (permalink) Old 07-06-2006
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The IAC is supposed to allow air to bypass the throttle body on startup when the car is cold. mine does the exact same thing and its normal. Because I dont like driving my car before I have let it warm up for a minute or two, I use that as my indicator. as soon as the idle drops down below 1000 RPM's, I start driving.
Now, if yours does that even with the car warmed up, that may be another issue, but it sounds normal to me.

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post #3 of 4 (permalink) Old 07-07-2006
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my car used to do that,and i mean it would idle high, like 2,500-3,000 rpm..i messed with it, tps, new iac,..still idled high, so i just unplugged the iac and left it like that..it runs perfectly now
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post #4 of 4 (permalink) Old 07-10-2006
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Maybe the coolant temp is reporting the engine is cold - so the IAC is bringing the idle up higher than normal. Test, measure, and if needed replace.

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