Mach 1 cold start slight miss

[albanygt40]

Hi
My Mach seems to have a cold start stumble or slight missifire when fast idling. Kinda pop pop in the exhaust and a slight rev drop. clears up when hot and doesnt miss when driving. Wondering if this is a common trait?

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[sakman84]

Diagnosing cold star problems can be a bit of a challenge. I wouldn't worry unless a Check Engine Light (CEL) was triggered. Keep in mind it is quite normal for your car to sound louder, and rev up more than usual during a cold start. Modern cars are programmed this way on purpose. Manufactures have even gotten busted by EPA because during cold starts the emissions exceed limits! In the defense of the manufacturer, they are just trying to get the car to start reliable, smoothly, and get it up to temp for efficiency. The rev drop you describe is a bit interesting.

If you want peace of mind, a shop with a proper ford scan tool and look into the ECU logs and look for misfire counts. Of course he can look at other parameters too for clues.
You are under warranty so if your dealer is competent, then you can give them a crack at it.

Does it happen every cold start?
Would it be easier to replicate by leaving the car at the shop at end of day, for a cold start check and scan the next morning?

That is how I would prefer to have it checked if it were mine.

Back on my first S197, I turned the key and the car didn't start, it kinda did for a split second, and then it died. Turned it back on again, no problem. I took it to the dealer for unrelated warranty work (rear DIFF leak TSB) and had them check out the stumble start. They could not find the problem. Never happened again.

Above all with something like this don't stress, you are probably totally fine and if it is a problem its likely minor. Good luck.

 

[melwff]

Hi
My Mach seems to have a cold start stumble or slight missifire when fast idling. Kinda pop pop in the exhaust and a slight rev drop. clears up when hot and doesnt miss when driving. Wondering if this is a common trait?

How many miles on the car?

 

[albanygt40]

Seems Ok now,I watch for it every cold start. Car has about 1500km on it. The car had sat for a while when it did it and had a few cold start short runs.

 

[Geofft21]

Seems Ok now,I watch for it every cold start. Car has about 1500km on it. The car had sat for a while when it did it and had a few cold start short runs.

Yes mine does to, sounds a bit lumpy after the initial start but soon clears ?

 

[Dfeeds]

Could be gas as well. I have rough cold starts when I fill up with 93 at the mobil by me (top tier station) but no issues when using the shell or BP, also 93 top tier. I also get the problem when on road trips where I don't have the luxury of being as picky about gas.

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