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Pontiac Forum: Idles fine until it get up to operating temperature?
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  #1  
Old June 2nd, 2018, 01:17 PM
oldandretired oldandretired is offline
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Idles fine until it get up to operating temperature?

04 Grand Am GT, V6. No trouble codes. Cleaned MAS air flow sensor, new air filter. Engine starts right up and idles fine when cold. When engine temperature gets to about 160 degrees or higher, the idle surges up and down, and the engine occasionally dies. Starts again with foot feed held slightly open.

'Have read dozens of posts about IAC's, but all indicated rough idle.

Is there a temperature sensor that tells the ECM to change parameters? Could this temp. sensor be the culprit? Thank you!
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Old June 2nd, 2018, 06:26 PM
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melsg5 melsg5 is offline
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I would suspect the IAC, remove it clean it and the passage it sits in. Could be a temperature sensor but you do not have any codes concerning temperature.
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Old June 2nd, 2018, 09:32 PM
oldandretired oldandretired is offline
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MelsG5,

I will clean the IAC valve and the passage way. I'll report back with the outcome. Thanks for your dedication to this forum!!
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Old June 7th, 2018, 01:17 PM
Zimgxp Zimgxp is offline
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It is going into Closed Loop when it acts up. I'd say IAC or Vacuum leak.
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Old June 16th, 2018, 08:54 PM
oldandretired oldandretired is offline
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Follow up - removed the throttle body from the intake and removed the IAC from the throttle body. The throttle body and IAC were beyond filthy. I scrubbed the entire unit in lacquer thinner and then used TB cleaner for a second scrub. I used strips of an old towel to scrub the passage way for the IAC.

Put a new Borg Warner IAC into the TBI and installed the unit back onto the intake manifold. Re-installed all the associated wiring harnesses. Disconnected the battery for about thirty seconds and re-attached.

Started up the car and the idle surged and declined. I immediately drove it for 16 miles at 40 mph (pissed off a couple drivers who came flying up on me) on a two lane highway. The engine now idles beautifully.

Thanks to this forum for all your help!!
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Old June 16th, 2018, 09:18 PM
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glad to hear you had a positive outcome
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