I've been fighting a rough running 1998 2.8L A6 Quattro (engine AHA) for a few weeks now. I can only get it to run by nursing the gas pedal. It immediately dies if I try to let it idle. The only error codes are P0300, P0304, P0305, P0306 (and one other for the ABS being unplugged).
The event leading up to this was the top nylon guide/shoe on the bank 2 camshaft tension adjuster broke off. After taking off the valve cover, I picked out all the chunks of nylon, removed the tensioner and replaced the nylon shoes on top and bottom and reset the cams in time. It looked like the intake cam was advanced by 1 tooth, which I assumed happened when the shoe broke. I didn't get any misfires at that time, but I was getting a P1392 for the short to battery positive on the bank 2 camshaft position sensor. I finally got that resolved by replacing the CPS. The car is stilling running the same, or maybe slightly better, after replacing the CPS but now the errors are misfires. I'm getting fuel (spark plugs are wet and smell of gasoline) and the spark plugs seem OK doing a rudimentary spark test. I will check the compression as soon as I can borrow a tester.
I wonder if the valves could have gotten bent when the cam was off by one tooth. From what I've read in this forum, others have been off 1 tooth, and not mentioned having bent valves.
I also wonder if the camshaft chain tensioner may be back. It's not stuck as I see it move up and down when I manually turn the engine. Other forum posts seem to indicate that the tensioner only plays a role at higher RPM's, and it doesn't seem like it causes a severe idle problem.
What else could be knocking out the whole bank 2 side, or do you think it could be the valves or tensioner?
I've borrowed a VAG-COM if anyone has suggestions on what to check. I'm a novice at the VAG-COM, but I'm starting to catch on about how it works. I have done the TBA already.
Thanks for any and all help.

 

Could your new CPS be misaligned on the cam? Did you inspect the mating surface of the cam to see if any damage was done to it? I guess bent valves is a possibility but doubtful. My timing belt tensioner broke and only bent 6 valves in 1, 2, and 3. Also very doubtful is all three of the coils are bad, you could swap all them over and see if the problem changes to your bank one side.

 

I'm sorry but I don't understand. Which "mating surface of the cam" do you mean? In any case, I did carefully check all surfaces and everything looks normal. Did you bend 6 valve stems? Were they intake or exhaust? I don't think it is the coils because I did a spark test on #5 and the spark looked very strong. Regarding the CPS being misaligned on the cam, it seems to be that it sits in only on spot. But I will try loosening it and seeing if it has any wiggle room in it. It will probably be Sunday before I can try though.
Thanks for the ideas.

 

i would probably recheck the valve timing. it will set miss fire codes if one of the cams are out of time. been there.

 

I bent 6 exhaust valves, I was thinking the CPS to be misaligned somehow just because your old one broke and could have caused damage.

 

I had just enough time to do a compression test tonight. Zero compression on 4-5-6 (about 190 on 1-2-3). It looks like my valves are bent on bank 2. I expect to pull the head this weekend. I'm a DIYer. I'm confident in taking the head off, but I've never replaced valves with hydraulic lifters. Will I need any special tools to work on the valves? Of course, I'm assuming that the pistons are OK - will have to wait and see.
Thanks

 

its cake work, hardest part is actually getting the head off. Make sure you stay organized, EVERYTHING goes back in the same spot, nice and clean. I used a magnet to pull the hydraulic lifters out so all the other lifters do not come out. Pistons should be fine. Get a good valve spring compressor, might as well replace the valve stem seals while you are there too. A tip when going all back together, dip the stem of the valve in thick oil and use a small slightly magnetic screwdriver to put the valve keepers back on. The oil will help the keepers stay in place.

 

Final update. I borrowed a videoscope from a brother and examined the piston heads through the spark plug holes. Each cylinder on the driver's side has a single impression from one of the intake valves. I think this supports my conclusion that at least one valve is bent in each of those 3 cylinders.
Although I would find the task satisfying, I've decided to donate the car to charity rather than repair it. My daughter has already bought a different car. My brother says the car is worth $500 at the most, if it is running (it's beat up pretty thoroughly). It's barely worth the expense of the parts at this point, and there's no certainty that it will run when I am finished. If she hadn't replaced it, I would go ahead and complete this fix; I think it would have been enjoyable.
Thank you all that contributed ideas to me. I appreciate your time and efforts.