CEL after changing spark plugs/coils.

[Nano909]

Hello Audizine, nice to meet you all.
This is my first post, and unfortunately it's about a problem I've been having.

The other day I was driving on the freeway and my A4 B8 suddenly started acting funny. The CEL and EPC lights came on. So I drove home and ran the codes.
It gave me P0351 and P0301.
So I went to my local store and changed out all four spark plugs and coils. I test drove it afterwards, and it worked perfectly fine. A few hours later, I drove it again, and it started misfiring and threw the CEL codes P0351, P0301, P0354, P0304, which is weird cause I had just changed the spark plugs and coils. It only starts misfiring and throws a CEL once I'm pressing the gas and it reaches over 3000rpm. If I drive normal, it doesn't misfire or throw codes. The CEL's are for the spark plugs and coils, which I already changed. I searched and searched and didn't find anyone with my problem. Once again, it only happens when I floor it and it reaches over 3000rpm.

Any suggestions?
Mods are APR stage 1 tune and a K&N intake.

[Nano909]

And now it just throws a p0301 code after I floor it.

[iChipster]

I have the same issue with the missfiring with only an apt stage1 no intake. I don't get any codes though. I'm going to bring it to a local shop soon and see if they can fix the issue and I'll update here.

[Nano909]

I have the same issue with the missfiring with only an apt stage1 no intake. I don't get any codes though. I'm going to bring it to a local shop soon and see if they can fix the issue and I'll update here.

That would be cool.
Today it just misfires, the CEL blinks, then I let off the gas and it goes away. Sometimes the CEL stays, and sometimes it just blinks and goes away. Weird.

[van462]

Check you plug gap. Set to .028. If the gap is larger then you may get misfire under boost. I prefer NGK copper plugs (BKR7E # 4644) over iridium plugs. Copper being a better conductor delivers a stronger spark and also conducts heat away from the tip faster lowering chances of preignition. I change mine every spring. I don't see any erosion on the electrode but they are cheap and change them and my air filter at the same time.

[Nano909]

Check you plug gap. Set to .028. If the gap is larger then you may get misfire under boost. I prefer NGK copper plugs (BKR7E # 4644) over iridium plugs. Copper being a better conductor delivers a stronger spark and also conducts heat away from the tip faster lowering chances of preignition. I change mine every spring. I don't see any erosion on the electrode but they are cheap and change them and my air filter at the same time.

The code I'm getting now is p0301. Only when I floor it and if it passes over 3000rpm. If the spark plugs aren't gapped to spec, it would cause a misfire like that?

[Nano909]

Bump

[van462]

Think of it this way. The spark is normally able to arc across the air gap. 14 psi is twice the atmospheric pressure. The cylinder volume stays the same so density increases. Its now the equivalent of jumping twice the distance. So changes in plug gap have greater effect. Most NGK plugs I have used come out of the box at .028. I rarely find one not at spec.

Not saying it will be a definite fix but is a no cost thing to check.

[Nano909]

Think of it this way. The spark is normally able to arc across the air gap. 14 psi is twice the atmospheric pressure. The cylinder volume stays the same so density increases. Its now the equivalent of jumping twice the distance. So changes in plug gap have greater effect. Most NGK plugs I have used come out of the box at .028. I rarely find one not at spec.

Not saying it will be a definite fix but is a no cost thing to check.

Yeah I agree.

[Nano909]

What are the possibilities of it being some sort of vacuum leak? Just checked the gap, and they're at .028.

[Nano909]

Bump

[Nano909]

Bump

[Nano909]

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[Nano909]

Bump

[Nano909]

Thanks for the help guys.

[ak11214]

Hello Audizine, nice to meet you all.
This is my first post, and unfortunately it's about a problem I've been having.

The other day I was driving on the freeway and my A4 B8 suddenly started acting funny. The CEL and EPC lights came on. So I drove home and ran the codes.
It gave me P0351 and P0301.
So I went to my local store and changed out all four spark plugs and coils. I test drove it afterwards, and it worked perfectly fine. A few hours later, I drove it again, and it started misfiring and threw the CEL codes P0351, P0301, P0354, P0304, which is weird cause I had just changed the spark plugs and coils. It only starts misfiring and throws a CEL once I'm pressing the gas and it reaches over 3000rpm. If I drive normal, it doesn't misfire or throw codes. The CEL's are for the spark plugs and coils, which I already changed. I searched and searched and didn't find anyone with my problem. Once again, it only happens when I floor it and it reaches over 3000rpm.

Any suggestions?
Mods are APR stage 1 tune and a K&N intake.

I have your exact issue. Just swap in ECS sparks/coil pack. The only different is my is stock. Did you fix your issue with re-gaping the spark plug?

[Nano909]

I have your exact issue. Just swap in ECS sparks/coil pack. The only different is my is stock. Did you fix your issue with re-gaping the spark plug?

I went with red R8 coils and new spark plugs from ECS, gapped the plugs to the recommended gap APR says for tuned cars, and everything came out better than ever.