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Discussion Starter · #1 ·
For the past few weeks I've been experiencing what seems to be a misfire / stumble / shudder at idle. Happens on cold start and at operating temp. It's much more noticeable with the AC running. I'm wondering if I'm experiencing the issue of carbon buildup on the back side of the intake valves. Does anyone else have an issue like this? I'm at about 25,000 miles.
 

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Is it constantly/heavily misfiring? Like, jerking the car? Or is it just a very slight hiccup occasionally while you're idling?
 

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I've felt that a few times while at idle as well. Usually right after start up but it goes away shortly after. I never really noticed the issue until I started running 87 instead of 93.
 

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I've gotten a very very slight rough idle after restarting the engine while it's warm after getting gas (only 93) a couple times (10k miles currently). I wouldn't call mine a misfire even, it's more like the PCM is sorting out fuel timing or something, and goes away once I start driving.

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Discussion Starter · #6 ·
I've gotten a very very slight rough idle after restarting the engine while it's warm after getting gas (only 93) a couple times (10k miles currently). I wouldn't call mine a misfire even, it's more like the PCM is sorting out fuel timing or something, and goes away once I start driving.
I don't notice this at all when driving, just while idling. Mine does not go away after the car gets up to operating temp.
 

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I would think if it was truly a misfire you'd see a check engine light. I would throw in some 93 and see if it goes away. Curious if its idling a little low and then when you turn on the AC, the draw makes it seem that the motor is stumbling.
 

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I've been experiencing the same issue with the AC on. Otherwise my idle is smooth. When the AC's on I've noticed that the idle seems a little low and when the AC compressor cycles on, the idle drops about 50 RPM or so. If I slightly push the throttle to about 700-750 RPM, the irregular idle stops. I tried seeing if there where any idle settings on my xcal 4, but there's only a setting for neutral idle which doesn't appear to change anything.
 
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Discussion Starter · #9 ·
I've been experiencing the same issue with the AC on. Otherwise my idle is smooth. When the AC's on I've noticed that the idle seems a little low and when the AC compressor cycles on, the idle drops about 50 RPM or so. If I slightly push the throttle to about 700-750 RPM, the irregular idle stops. I tried seeing if there where any idle settings on my xcal 4, but there's only a setting for neutral idle which doesn't appear to change anything.
I'm wondering if there is a PCM or other software update that may take care of this. It's under warranty still so I guess I'll take it to my dealer. Mine is not completely smooth with the AC of but probably about 95% of the rough idle is gone.
 

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Mine does it occasionally its like a real rough idle where you feel it "bouncing' a bit. yeah ford said they've never heard of that issue all though it happens quite frequently but then goes away. PCM idle relearn did nothing to really fix it. It could benefit from stronger motor mounts.
 

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I used to use 87 octane and my Sport Fusion never used to run exactly as smoothly as I would have liked. But... for the past 6 months, all I put in is the highest octane (either 92 or 93, depending on the gas station that I go to) and the car runs so much better. And interestingly, I get much better gas mileage.
 

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I don't care what anyone says, if a car has a turbo or a supercharger it needs higher octane gas. I have had many of each in the past and this is the first one that has not called for at least 91 from the factory...
 

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I actually came on the site today for this issue. I am at 20,000 miles now and this is happening at idle speed in traffic with brake off and AC on. I just starting running regular gas instead of premium on my current tank. The car almost lurches forward with every throb of idle albeit very minor. Funky feeling.
 

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Mine started doing this today, except mine died a couple of times at idle. I am tuned, but this is the first time I've seen this. There are no fault codes when this happens or when it stalls.

I tried removing the tune, but it still does it.
I've also got the TL catch can and Gfb diverter valve installed.

Things that make you go hmmm...
 
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