Ford Mustang Forum - View Single Post - misfire at idle when warm
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post #1 of (permalink) Old 07-12-2019 Thread Starter
NAs197's Avatar
Joined: Sep 2016
Posts: 78
misfire at idle when warm

Hi All, I have been battling this problem with my 07 GT for the past couple months. When I first start the car it idles fine, but as it warms up it starts to have a misfire at idle (the engine shakes and I can feel it in my seat/steering wheel so I believe that's a misfire). When it misfires the idle drops down a bit. The car has not stalled on me. I feel no loss of power and under any type of load it runs perfectly smooth. i do think though that my mpg's have gone down. I have done the below:

No codes
Spark plugs were replaced 17k ago before the issue occurred
Just cleaned throttle body, MAF, Air intake and ran fuel injector cleaner
Seems to settle a bit when I turn the AC on but still has issues
Will settle a bit when I give it gas but rough idle will return
Did idle relearn
Cleaned crud around negative terminal but some of that blue stuff is still there
Unplugged VCT sensors, started car still and still had the idle issue

Mechanic hooked up a smoke machine to find leaks, thought that certain injectors may have been leaking and replaced some seals. He also drove the car while hooked up to his computer and didn't find an issue with any coils. I told my mechanic to check the alternator and he didn't say it was bad so i'm assuming it's fine. Also when the car sits for a month it starts up immediately like a brand new car would so i feel like it's good. Haven't checked the TPS sensor yet but I doubt that's it because I feel like that wouldn't cause the engine to shake/misfire.

I have datalogged the car and If someone who understands that stuff can/wants to read it please send me a message with your email and I'll send it right over. Any help is greatly appreciated. I am trying to sell the car and it would really help if I could get this issue fixed before selling it.

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