01 Gt Cold Start Idle Fluctuation?

NRB Auto

New Member
Jul 23, 2015
I have a 2001 GT, NOT ALWAYS but usually only in direct morning under "cold start" conditions I will get a high idle of 1,600RPMS. Now and then if you put it in gear it will drop RPMS and die out. If you restart the mustang right away idle will return to normal. If not about every 30 seconds or so it will drop idle down to 1,000rpm for a short time then go back up fluctuating for about 10 minutes while idling. I have cleaned and tested the IAC and cleaned out all intake related parts. I havn't been able to use my Ford Diagnostic Software because I never have my car in my shop during a morning start. Any idea's?

Also currently it only has 3.73 gears, no tune or any modifications. High idle sound comes from ehaust but you can also hear a drone from the Air housing.
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Active Member
May 10, 2015
Marion Ohio
Thats a hard one... In my experience a problem like that and the drone your talking about is normally cased but the Air/Fuel mix being off or even a little out of time... Id say its probably running real rich or lean when you first start it up probably rich and then the ECU adjusts to compensate... There are lots of things that could case this but id start by checking the M.A.F.sensor , Air Temp sensor, and even the o2 sensors...
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