Engine misfire. One off event, all clear now??

[GabrielSyler]

Hello

I had just been driving enthusiastically for about 30 minutes. Twisty sections of road with lots of accelerating/braking with the engine sitting at around 4000-6000rpm through the gears. The The EPC light came on and the engine then started to misfire, with a noticeable loss of power. I drove for about 5 minutes to see if it went away but it didn't (no where to pull over anyway). It was also misfiring on idle when I'd pulled over. My Torque pro app came up with a "P0302 - Powertrain, Cylinder 2 Misfire Detected" fault. It didn't flag up any other issues.

I turned the engine off, checked the engine, gave the coil leads a shake and started the car again. The EPC light remained on (same fault) but the misfire had gone. Drove for an hour (to return home) with no misfire. I wasn't driving as hard, low revs with the odd burst of acceleration. Got home, turned engine off and on again and the EPC light had gone.

The car is a 2013 B8.5 S4 with APR stage 2 , APR TCU, AWE exhaust and an intake. Its got around 30,000km on clock. It had recently -less than 500km ago- had a minor service with an oil change.

I've tried searching the internet, but most have come back with fixes for a permanent fault (ignition coils, sparks etc).

I'm going to have a look at the spark plugs, but since it seems to be back to normal, I'm guessing it might have been caused by something else. Any ideas before I start replacing everything?

Thanks

[b8s4me]

I had the same issue on my A4, and on my S4 I woke up to a "differential" fault which went away after I turned it off, then back on never to be seen again.

If I were you, I would change all the spark plugs and gap to .028 if stage 2, .032 if stock and I would swap cylinder 2 ignition cool with the one next to it. If you get an EPC and it's not cylinder 2, it's more than likely the cool. If it stays with cylinder 2, maybe wiring, or clogged fuel injector, possible carbon buildup causing major air blockage or something else.

[GabrielSyler]

Thanks I'll give that a try

[abamfo]

I had the same issue on my A4, and on my S4 I woke up to a "differential" fault which went away after I turned it off, then back on never to be seen again.

If I were you, I would change all the spark plugs and gap to .028 if stage 2, .032 if stock and I would swap cylinder 2 ignition cool with the one next to it. If you get an EPC and it's not cylinder 2, it's more than likely the cool. If it stays with cylinder 2, maybe wiring, or clogged fuel injector, possible carbon buildup causing major air blockage or something else.

Can you explain how this helps and why stage 2 should be gapped differently? I have not heard of it, that's all

[Mat@1975]

Hello.
Maybe a leaking SC heat exchanger. It happens sometimes on this engine.
Perhaps those Who experienced it Could chime in and expose symptoms more in details ?

BR

Mat.

Envoyé de mon SM-G850F en utilisant Tapatalk

[abamfo]

Hello.
Maybe a leaking SC heat exchanger. It happens sometimes on this engine.
Perhaps those Who experienced it Could chime in and expose symptoms more in details ?

BR

Mat.

Envoyé de mon SM-G850F en utilisant Tapatalk

There are a couple of people who have had cracked SC intercooler cores also but I don't know how either causes misfires but would like to know actually. Is it through leaking coolant into the manifold??

I have a misfire issue and rough idle issue, and have pretty much replaced half the ignition system to no avail, I don't recommend that approach!

Misfire reasons I've researched for our cars: carbon buildup, bad fuel, spark plugs, a/f ratio sensors, fuel pump, clogged cats

[GabrielSyler]

spark plugs and a spare set of ignition coils are on order. Will be able to check the existing plugs the weekend and report back.

[Loe]

in regards to the leaking intercoolers, once it leaks, it'll spray coolant directly into the intake ports, fouling the spark plugs once it reaches into the cylinder. Mine was directly on cylinder #5, it first was only under WOT conditions, however it quickly fouled that plug. The plug itself was wet, with a white moldy-looking texture to it. It was hard to identify though as it was on the top of the intercooler, which can only be visibly seen once you remove the intercooler from the S/C.