2001 Mustang V-6 5 speed, misses and backfires only when engine cold

[DeFormula]

EGR code, replaced EGR and cleaned DPFE (?), check engine light still on. Cleaned MAF, cleaned IAC, haven't been able to find any vacuum leaks. Haven't checked plugs or wires but if they were bad, wouldn't it do the same even when the car warms up? Anyway, plan to check those. It has a cold air intake and true dual exhaust, with a small leak that seems to dissapear after a couple minutes.

I think it is a sensor related problem occuring when the car is cold (open loop?). Anybody know what this could be or have other suggestions? If you know someone that is a driveability genius that won't break me let me know. Thanks in advance.

Dave

[MarkVIII93]

I've heard of a cracked coil pack allowing moisture and causing issues.


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[DeFormula]

I've heard of a cracked coil pack allowing moisture and causing issues.

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I thought about this also. I have not yet checked the coil pack with a voltmeter, but I pulled just a couple plug wires off and they were greasy. I don't know if they are supposed to be greasy, or if the coil pack is oil filled and was leaking (???) Anyway, one of the biggest problems I have is my son is driving this car, and he is rarely home when I am so I can't work on it !!!

Thanks for your input.

[MarkVIII93]

Like die-electric greasy? The bottom sides of the packs are known to crack on the 6 cylinders so you may need to remove it to get a good look.


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[DeFormula]

Like die-electric greasy? The bottom sides of the packs are known to crack on the 6 cylinders so you may need to remove it to get a good look.


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could have been die-electric. Ill keep you posted as I delve deeper into this.

[TooSlo86]

Is the check engine code saying lean condition detected? I bet it's lean when cold, once it warms up it's getting enough fuel that it's ok. How old are those 02's?

[DeFormula]

Is the check engine code saying lean condition detected? I bet it's lean when cold, once it warms up it's getting enough fuel that it's ok. How old are those 02's?

I'll re-check. Only code so far was EGR. What you're saying makes sense though. This is a very clean, low mileage (73,000) car. I think nearly everything on the car is original...plugs, wires, fuel filter, O2s, etc. Just based on age alone it needs to be gone through and have all of these basics taken care of too. We just bought the car a couple of weeks ago and did brakes and some other items that needed more immediate attention. But as I say it runs really strong once it's warmed up.

[Ponyryd]

Agree it sounds like a vacuum leak, honestly though you'd probably be best to drop it off somewhere to have it diagnosed than to just throw parts at it.
The DPFE is likely the cause of your egr code, the valves themselves rarely fail.
Take a GOOD look at the cold-air for leaks, spray the joints with brakeclean or WD-40 and listen for a change in RPM, same goes for the intake. Often the seals between the upper and lower cause this issue, and being that it has some go-fast parts maybe someone has been playing in there.....
This could also be low a fuel pressure problem, needs more fuel when cold, get a gauge on it and see what its at.
Coil/tune up parts would not cause this. Yes the coils crack, easily checked by spraying with water-if it starts misfiring, the coil or wires are bad.

[DeFormula]

UPDATE: I tell my son to be home tonight because I want to mess with the stang. Tonight he tells me that it has started missing all the time now, just much worse when its cold. He also said it has stalled a few times when it is warmed up. We go for a test ride and I definitely feel hiccups. For the heck of it, we pull the coil off and sure enough it is cracked on the back. Put on the new one from O'Reillys and it runs perfect. Lug it down, wind it out, part throttle, no missing. Now, we have to wait to see what happens tomorrow morning when he fires it up cold. I did not pull codes again tonight but a few days ago the ONLY code was EGR.

[Ponyryd]

Great! Although in dry weather it shouldn't make much difference if it was hot or cold, it was probably worse due to the rain today, regardless I'm glad its running better.