I just bought a 1999 A6 2.8 30v with 177000 miles it passed emissions a week before I bought it but between the pass and me buying it the CEL came on. I know the code is for random misfires on bank one (cyl 1,2,3) I already replaced the coil pack for all 6 cyl but it has NO EFFECT even after clearing the code. The plugs and wires are all newer and to me the valve cover gasket on that side looks new as well (different color and much newer looking than drivers side)

It seems to run just fine tho, the only time the CEL flashes is when going up a decent hill and even then I notice NO hesitation or skipping. Ever once in a while it will idle rough but that's it really.. can I drive it like this? I don't care if the cat gets destroyed honestly I won't have the car when it's up for another emissions check. But I NEED to know how to fix this because I have to drive this car daily to work I have no other options. Any help would be appreciated. I have checked for vacuum leaks or things of that nature and all fine. Battery and alternator are all good. I'm thinking timing chain tensioner but have no idea really please help a noob Audi lover out! thanks in advance for any help!!

 

Oh and if we're thinking its the tensioner how much will that cost at a shop, labor only?
Or aprox cost for any fix you might suggest lol thanks again!

 

Since you misfires are all on bank 1, likely problem is with ignition control module for that bank. On my 2.7 there are 2 ICMs. One for each bank. They are the same p/n, so you can swap left to right to see if misfires follow the module. If so, then ICM is bad.