Coyote Rough Idle

[Bullitt0819]

Got the rough idle again today. About 100degF and sitting at a stoplight with Max AC I feel the roughness and idle goes up about 100RPM, this time running a tank of Chevron's finest (91-octane), so I can't blame the Costco gas.

Here's another issue I have that, as far as I can tell, is ambient heat-related (doesn't Ford test their cars/engine in hot climates?!). Looks like a trip to the dealer is in my future:

https://www.mustang6g.com/forums/threads/ghosts-in-the-machine.125514/

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[Andy13186]

Have you used ceratec? Have you ever used e85, or have you always been on the stock tune? do you have a catch can? also what oil do you use? I am trying to find some similarities in the cars that have this problem. I do have a catch can, ive used e85, amsoil 5w30 and 0w30, and I have used ceratec.

I still have the same problem although it seems to be getting less severe and less common. I kind of think it may be an o2 sensor or spark plugs. I dont think the dealer can do anything without a check engine light going on but cant hurt to see what they say I suppose. Keep us updated if you do find a cause or solution. The o2 sensor didnt fix my issue despite having had a code for it and getting it replaced my car stalled on the drive back from the dealer on the stock tune but hasnt stalled since and no light has come on again.

 

[ChromaticGrey]

Every now and then while smoothly idling at a light, I'll feel the car kind of shudder, or rumble a bit. Almost like the torque of the whole car chassis when you rev an engine, but very light. And it's for a moment, a quarter second at most. Then back to as it was. No movement on the tach.

 

[Stangnut]

Got the rough idle again today. About 100degF and sitting at a stoplight with Max AC I feel the roughness and idle goes up about 100RPM, this time running a tank of Chevron's finest (91-octane), so I can't blame the Costco gas.

Here's another issue I have that, as far as I can tell, is ambient heat-related (doesn't Ford test their cars/engine in hot climates?!). Looks like a trip to the dealer is in my future:

https://www.mustang6g.com/forums/threads/ghosts-in-the-machine.125514/

No. At least not very much. If they did, the upper seat coolers would work and the AC would be a LOT better. Oh and you probably wouldn't be having your problems either.

 

[GreenS550]

This is my 3rd coyote Mustang. It might increase idle if the computer says it needs it. I am thinking that the faster idle is normal. My other '11 which was nearly flawless for 25K miles with a Roush on it would do that. The other thing I'm thinking is that when the idle increases, does the fan kick on as well? The faster idle in my tuned Bullitt and tuned ecoboost Explorer run the fan more and the idle increases as well. Perhaps to move the coolant faster through the radiator. Just wondering. But all my Mustangs including the '05, 07 and 09 Bullitt had tunes which caused the idle to increase when it was hot.

 

[Bullitt0819]

Have you used ceratec? Have you ever used e85, or have you always been on the stock tune? do you have a catch can? also what oil do you use? I am trying to find some similarities in the cars that have this problem. I do have a catch can, ive used e85, amsoil 5w30 and 0w30, and I have used ceratec.

I still have the same problem although it seems to be getting less severe and less common. I kind of think it may be an o2 sensor or spark plugs. I dont think the dealer can do anything without a check engine light going on but cant hurt to see what they say I suppose. Keep us updated if you do find a cause or solution. The o2 sensor didnt fix my issue despite having had a code for it and getting it replaced my car stalled on the drive back from the dealer on the stock tune but hasnt stalled since and no light has come on again.

I do have a catch can--get a teaspoon or so of oil every 1K miles--but other than that I'm bone stock and I've only put the Motorcraft 5W-20 in it (free oil changes at the dealer). No codes (yet). Increasing the idle a bit I can understand, but the roughness doesn't compute; the engine is very smooth otherwise across the RPM range.

 

[Tony Alonso]

Yes, I've experienced similarly under similar conditions. It seems to disappear after getting back up to speed or reducing the AC load. It's happened 3 times in the last 2 months.

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