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Disappearing misfire when warm on cold days


Stealth-T

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  • Member For: 5y 2m 2d

Hey folks. From my searches all over I couldn't seem to find an answer, so I was hoping someone might be able to point me in the right direction. After developing a misfire at high RPM, it was determined I had a bad plug or two and they were all replaced and gapped to .7mm just like my previous plugs. All was dandy. Day after I found it misfired just as it was getting warmed and the error symbols came up on the dash. However when I pulled out the xcal4 and tried to scan for errors it was gone and the error did not re-occur for the rest of my drive. This is where the annoyance begins. It only happens on cold days where it's sub 10 degrees outside temp. and when the car hits a warm point. After turning the car off and on again the misfire/error does not re-occur and the couple times I've tried to scan for codes there has been nothing that has come up. I know the coils are perfect so it isn't them. Does anyone have any clue as to what might be causing this? Proving very annoying to narrow down:help:

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  • Member For: 15y 11m 18d
  • Gender: Male
  • Location: Melbourne

how do you know the coils are perfect? if they're not OEM coils, I'd be checked those first.

 

is the car tuned?

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  • Member For: 5y 2m 2d

Coils are perfect because I just replaced them as part of my general maintenance and it made no difference to the misfire. And I made sure to get brand-spankers from Ford!

 

Ya I had it tuned a couple years ago. Do you suspect tune isn't happy?

Edited by Stealth-T
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  • Member For: 4y 8m 27d

Hey mate, check the wiring to your cam sensors at the back of the motor. The wiring often melts and causes misfiring. Given where yours is breaking up though, it's probably something else like CAS. Assuming your coils, coil plug wiring and plugs are fine... 

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  • Member For: 5y 2m 2d

Cheers mate. I'll give cam and cam angle sensors a double check. I'm pretty sure the coil wiring was fine as I did give it all a quick once-over. But I'll double check. Just find it really strange that it only does it on cold days. So wouldn't think it'd be wiring unless there's a ridiculously tiny gap in there.

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  • Member For: 15y 11m 18d
  • Gender: Male
  • Location: Melbourne

the tune could definitely be suspect with a hot/cold issue. but it's unlikely in comparison to a mechanical issue causing it to compromise a few tune parameters.

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