2007 A6 4.2 Strange Mis-fire: Codes included in post and YouTube video! Scrap it?

[sgfreak96]

Hi all. I made a hilariously DUMB mistake: I spent $2700 on a 2007 Audi A6 with a glorious 4.2l V8 and... 190,400 miles. I did not think the fees would get so out of hand, and I was itching for a new car to toy with and have bought a true hoopty.

This car has a failing torque converter, as evident by the bouncing RPMs, but my MAIN CONCERN with the car is it has misfire codes, please see below!!!


210266


These misfires are not always present, at least, it does not always seem that way. From a cold start, the vehicle turns on and seems to run fine and drive ok. I can drive the vehicle for a long distance without issue, so long as I don't go to high load situations - I'm talking like 3/4 throttle or more. Once I give it the beans, the car throws a flashing CEL, and the car misfires very badly. The strange thing is if I then revert to driving like a grandma and light throttle it everywhere, the misfire remains and can sometimes be quite bad on light throttle. If I park and shut the car off, and restart, the car is totally fine again, and can be driven around up to half throttle or so like usual... unless I give it hard gas and the cycle repeats.

I find it very strange the car remains misfiring after resuming light duty driving, and then goes away upon restarting. What would a restart do to magically make the car run right? I would normally have assumed coils or sparks, but the fact it runs fine on light duty, misfires on hard accel, and then remains missing on light duty is very puzzling to me.

Anyone have any ideas with what to try? I'm going to do an Oil change, and new spark plugs this weekend. I am also going to swap the coils around different cylinders to see if the codes change. Fuel filter was another thing I thought of replacing. Please review the codes and symptoms and let me know your thoughts please!!!!

Video for your entertainment:
https://www.youtube.com/watch?v=C3QwMBjUiuY&lc=UgxAVGU1XLE2L47urkl4AaABAg.9H6NZcE3gh-9H6UIRz3CzN&ab_channel=sgfreak96

[BB6-B6]

Lol I’m in the same boat. Bought a 2008 a6 4.2 fully loaded with 200k does the same exact thing but on a cold start I feel the misfire sometimes epic light comes on while it warms up. But if I shut the car off and start again it’s fine. Once a misfire is detected I believe the coil or injector is disabled to prevent more damage and stays that way. I’m leaning towards carbon build up but wont know till we get some better weather out here. I’ll let you know what I find


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[sgfreak96]

Thank you for the reply!! That would be very interesting if the injector/coil gets disabled to prevent damage, but that would exactly match my symptoms. Mine also struggles to start sometimes even when warm, which leads me to believe bad fuel filter might be plaguing it. Carbon build up is another fun problem. I'll probably list mine for sale just to see if anyone bites, but if I keep it I'll entertain myself with maintenance until it inevitably blows up! Does your car have records of the timing chain guides being done?

[BB6-B6]

I finally got a chance to work on the car, pulled the manifold to see how bad the carbon build up was. It was terrible lol full of carbon. I’ll update you on what happens after it’s back together


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[BB6-B6]

If you do post it for sale I’d be interested lol


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[BB6-B6]

215245215246


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[sgfreak96]

If you do post it for sale I’d be interested lol


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I have it for sale listed now on facebook. Someone coming to look at it Wednesday, but not sure how serious they are. You're welcome to come get it if you want it haha. Very curious if carbon cleaning fixes yours!

[sgfreak96]

I should also say, I suspect a clogged cat may be the issue. In neutral, if I rev it, 0 misfires or stutters, and revs very quickly and happily. But under load, it really bogs down if I floor it or give 3/4 throttle. Yesterday, it almost felt like it was lightly misfiring and just hesitating to accelerate. In the past though, it would misfire much rougher though.

[sgfreak96]

Another update, yesterday I drove it for an hour, and decided to give it some hard accel. Car actually downshifted and wound out through to redline with only light stuttering. When I first got it it was stutter terribly and break up very bad. Somehow it's improved over time.

[BB6-B6]

Big difference in power now after the carbon cleaning. But still misfires on hard acceleration but the now I can definitely feel it coming from the tranny slipping. I added the dr tranny instant shudder fix and the right away felt a difference I’m able to accelerate way harder than before. I ordered new trans fluid, hopefully this will resolve the issue if not I agree with the cat being the next thing to look at. Previous owner stated they replaced cats from dealer.


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[BB6-B6]

Send me a link to the ad


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[sgfreak96]

PM'd the link. Also FYI, car really only seems to misfire badly when at full operating temp. Very strange, I'm doing a scan with an obdeleven tomorrow so I'll see what happens. I cleared the codes posted earlier and have been driving it for about a month, so we'll see what codes appear. If Cyl 1 and 6 misfires are present again with no others, I'll feel confident maybe it's coils - and I'll swap them around.

[sgfreak96]

welp, I sold it! No more worrying about that anymore [:D]

[Fisher1]

Don't you regret it now?[;)]