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Misfire after cold start

metalhead79

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I installed pre-gapped Denso ITV22 spark plugs about a month ago. Friday my check engine light came and stayed on for about 30 miles. I had the code checked and it was "P0300 Random misfire". It did not indicate which cylinder. I had noticed after I installed my exhaust a slight miss in the mornings when I would start her, but didn't think much about it. The stock exhaust was too quiet to hear. I started to really listen after I pulled the error code. Today I was listening after a cold start and noticed that it misfires until the engine warms up and then seems to go away. After getting home from work (45 minute drive) I listened for a couple minutes and didn't hear any misses.

Is this an issue with the Denso plugs on my non-tuned EB? Should I roll back to the stock plugs?
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EAndre

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My ecoboost has always had a slight miss fire on cold starts and now after all the upgrades and tunes it's still there lol I never gotten a code for it though
 

jrock

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Did you check the plugs?
 

Joemomma22

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i doubt its related but when i had a code for p0300 my dealer told me it was a fake code and that the pcm needed to be updated. just take it in for service.
 

EAndre

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Did you check the plugs?
Na it's been doing it since the car had 7 miles. Then after 5k miles I did all the upgrades including plugs and it still does it. Also my data logs show perfect ignition corrections on all 4 plugs.
 
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metalhead79

metalhead79

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i doubt its related but when i had a code for p0300 my dealer told me it was a fake code and that the pcm needed to be updated. just take it in for service.
I'm doing that tomorrow. If there is something wrong it'll be fixed under warranty.
Little tired of taking it in to the dealer. This is the 5th time since I bought the car.
 

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EAndre

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I'm doing that tomorrow. If there is something wrong it'll be fixed under warranty.
Little tired of taking it in to the dealer. This is the 5th time since I bought the car.
make sure you stick back the motorcraft plugs
 

Btor23

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i doubt its related but when i had a code for p0300 my dealer told me it was a fake code and that the pcm needed to be updated. just take it in for service.
Had the same problem. car idles the same but does not throw a code anymore :shrug:
 
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I had a built motor put in and now I get the same thing. Its only on the occasional cold start. I clear the code and its fine for a couple days. I don't think its anything to worry about, but it sure is annoying.
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