Thoughts on EPC light and these faults...

B8 S4
#1

Drove the car to a fantasy football draft tonight and drove pretty mellow for the most part only a few WOT blasts… The car drove fine there but when I left the epc light came on and the car shuddered badly and I could tell it was down on power… Drove a mile or two until I found a safe area to pull over and shut the car down… waited maybe 30 seconds and started the car but the epc was still on and I didn’t have the laptop to run a scan… Took my chances as the temp of the car was fine and no CEL just the epc light… Just got home and ran a scan and got the below…

2 Faults Found:
6352 - Cylinder 3
P0303 00 [100] - Misfire Detected
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 13812 km
Date: 2014.08.24
Time: 21:55:08

7948 - Cylinder Disabling
P130A 00 [109] - -
Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 13812 km
Date: 2014.08.24
Time: 21:55:08

Just did a quick search and browsed a few threads but will read more on Monday as I’m tired… I guess it could be a number of things, coil pack, spark plug, sensor, etc. I’ve had misfires once or twice in the past but never got the cylinder disabling that I can remember… I have a vacation day tomorrow anyway, so I’ll flog the car and see if it comes back… Any thoughts?

#2

The positive side is those codes are from today. So its not like it was a stored code in the ECU.

#3

This happened to me prime when I was experimenting with methanol amounts. Sprayed too much and got misfires and 2-3 cylinders disabled.

Pulled over, restarted car, ran fine.

Got home, cleared codes, never came back.

Now I know what caused my misfires, your priority should be finding out WHAT caused your misfires.

Only a few things:

Spark plugs
Coil packs
Bad fuel(doubtful)

You can pull plugs and look at the tips, see if you notice anything unusual in said cylinder, also, you can swap coil pack to a different cylinder and see if problem ever comes back.

By chance did this misfire happen at the top of fourth gear?

#4

Thanks guys…

Yeah, I always scan the car after every visit to the strip and every month or so in general trying to be proactive… This time it was a noticeable issue so I knew something was up…

Jeff, Yeah those are what I figured also after I seen the error but it seems a few have had other issues as well and I’ll spend some time today reading more and seeing what I can find… Just hoping it’s nothing more serious…

I was not at the top of 4th, again as this happened on the street… I was in an area I don’t know at all and it was on a rural road as I was heading back to the highway, I was in 5th just cruising and realized I needed the turn that was coming up, so I down shifted to what I thought was 3rd… I then started to make the turn and realized it was much sharper than I had thought so I downshifted again and hit the brakes so I didn’t go off the road, but I was in 2nd and not 3rd so the car instantly redlined… That’s when the light came on… It was a high g turn for sure and hitting the redline may have caused a sensor to freak? The car then shuddered and drove pretty bad thus me pulling over and turning if off and back on… I figured if it didn’t restart I’d just call a tow truck but it did and the temps were fine and no CEL so I drove it home and it drove fine but the EPC stayed on… I cleared it so will see how it does over the next few drives… If it happens again I won’t clear it and will check the plugs but most likely just let the dealer fix it… I still have the warranty as they extended it with the whole t-stat and water pump issues and my dealer is great so they’ll fix it regardless of my mods… Hopefully, it was just a one time thing…

#5

Not that it’s comparable, but I constantly down shift into 3rd/2nd at high speed while threshold braking at the track and have never gone into limp. Although my redline is much lower :frowning:

I would assume at this point you weren’t even injecting fuel since you were engine braking hard. Although the blip to rev match might have been responsible. Assuming you were on the 93 file with 93 in the tank?

It could be a small bug in the beta ____ software I’d guess? Maybe the some of the factory safeguards on the overrev protection have been slightly modified? Hard to say. Would be interesting if you can recreate the problem once you clear codes.

When I had water in my gas tank, the cylinders that misfired and subsequently deactivated created the massive crank imbalance and vibration.

#6

drob, 100 file with 100 octane, GT260… We think a like as that is my plan today to try and recreate so to say but with vagcom logging… Hopefully, it was a fluke… The car ran like shit trust me and at first I thought maybe one of my cats was the problem but the car chugged too much and power was way down… I didn’t try to beat on it though until after I shut it down and even then I took at easy until I got close to home…

#7

I had the cylinder misfire issue a few years ago, and my injectors were replaced under warranty. Seems to be a common issue with our cars.

Btw I wish I had your dealership - would have come in handy a few months ago.

#8

You can see that two people had similar issues in a thread I posted a few years ago. One guy had his HPFP replaced and another had his cam shaft sensors replaced. It’s interesting all the various things that can result in misfires being detected.

http://www.audizine.com/forum/showthread.php/458919-Misfires

-Skid