2007 S4 Misfire after hard pulls

[07s4]

I have a 2007 S4 6mt, I haven't owned it very long, but the other day I went out to a deserted road and did a couple pulls, not launching, probably 10-100. After the second one it felt like the engine was misfiring, but I didn't get any check engine lights or anything. I turned the car off and turned it back on and the roughness went away, which I thought was weird. I tried to duplicate the problem, and It came back, not every pull, but usually after two of them. It always goes away by restarting the car, I wasn't letting the car sit between turning it off and turning it back on, I cycled the ignition without hardly a pause. The car is completely stock.

I have decided that since I don't know how long its been since it has had preventative maintenance performed on it, that I would at least check the plugs, and they didn't look terrible, but I did discover a leaking valve cover, which I will replace along with the plugs for good measure. I will also order a fuel filter and air filter and a serp belt at the same time. I was reading about punching the primary cats, I might do that too, but I would rather chase the problem on a factory car, unless there is a chance something could have gone wrong with the cats to be causing this?

Does anyone have an idea what could be causing the (I don't want to call it a misfire because its not throwing a code) "rough running" after high load, high rpm operation? Is there anything else I should replace while I am in there?

Thanks

[RedS4avant]

I would get new coils and plugs if I were you

[emilio]

have you tried pulling OBD codes or DTCs from it, anyway? i would expect a period of misfires to turn on the CEL, but sometimes you can get very brief problems that only register as "pending faults" and don't actually turn the CEL on.

- emilio

[jmcS4]

it could be your cats but that will usually throw flashing CEL if they are clogged when you go WOT. i had that issue when i bought my S4, the PO actually told me about the issue and i bought the car hoping it was just clogged cats, and it was.

[07s4]

I would get new coils and plugs if I were you

This seems to be the trend. What part number should I be looking for? I've seen a few threads about the coil packs being updated, I want to make sure I get the right version.

have you tried pulling OBD codes or DTCs from it, anyway? i would expect a period of misfires to turn on the CEL, but sometimes you can get very brief problems that only register as "pending faults" and don't actually turn the CEL on.

- emilio

So I drove it again today and got some DTCs...

P0431, Catalyst 1 Efficiency below threshold Bank 2
P0300 Random/Multiple Cylinder Misfire
P0302, P0303, P0304, P0305, P0306, P0307, P0308 - Misfire codes for cylinders 2 through 8.

I cleared the codes, and did a few pulls, CEL didn't come back steady, but did flash 12 times.

it could be your cats but that will usually throw flashing CEL if they are clogged when you go WOT. i had that issue when i bought my S4, the PO actually told me about the issue and i bought the car hoping it was just clogged cats, and it was.

Could a misfire cause clogged cats? Or do the clogged cats cause a misfire?

This all only happens when I hoon the car, driving around normal you would never know anything is wrong.

[jmcS4]

Could a misfire cause clogged cats? Or do the clogged cats cause a misfire?

This all only happens when I hoon the car, driving around normal you would never know anything is wrong.

well i'm not going to tell you the first thing to do is gut your cats, but theres a possibility it might be the case. Yes misfires can destroy your cats and clogged cats in turn cause misfires and flashing CEL at WOT or for me going over 4Krpm with moderate to heavy throttle

[draggingto]

This sounds pretty much exactly like what my car does also. Feels like it just runs out of steam sometimes above 5k. Then will flash the CEL. Shows pending misfire codes on two cylinders 4 & 6. I also get a CEL for warm up efficiency catalyst below threshold Bank 1&2 this is constant. But the car drives normal if you don't beat on it. Could it be plugged/bad cats or pre cats?

[draggingto]

Bump for more opinions

[eddiedellz]

Any developments?

Sent from my SM-N920V using Tapatalk

[willnando]

My car did the same thing after some pulls.. Even got rough idle one day, sounded like the car just wanted to shut off. I go through the gears with hard to medium throttle and it hiccups at times. No cel..

I need the hex-USB+Can VCDS cable to scan it and at the nice price of $340, its either replace all coils/spark plugs for about the same price or pay for the cable and look for codes..