I have a 2000 A6 2.8 quattro with 136k miles. I had misfires @ 8 months ago, had an independent tech replace a coil pack, had misfires again. again replaced a coil pack (with warrantied part) as they thought it was a part failure. again misfires started. misfires were inconsistent. Have had CEL on, sometimes flashing, as well as ABS, brake and Air Bag lights. misfires got worse, especially in idle and lower gears. eventually smoke emerged from under the hood and through the air vents. I was told by dealership that I need new cats, but they can't say how they know this. Took to independent with a factory diagnostic and have 13 fault does--warm up catalyst; bank 1 and: efficiency below threshold; ignition coil power output 1, 2 & 3: electrical malfunction; rough road/engine torque signal from ABS: electrical malfunction; Randon/Multiple Cylinder Misfire-cylinder 1 & 6; secondary air injection sys, bank 1 & 2: insufficient flow; power supply terminal 30: voltage too low; crash signal from airbag controller: implausible signal. my questions are: what is the likely cause of the misfires and also the smoke (which only happened once when the car was close to dying)? if I replace cats will this fix my performance issues? how much should this cost? what else would you recommend repairing? how much would repair costs be? should I sell and move on? if so, who would be interested in purchasing? thanks for any help.

 

Geez, sounds like a lot of issues, I need an oxygen sensor and it threw a similar code to one of yours, the warm up catalyst thing. What I recommend is that you re-post this in the A6 section of the forum, no one ever checks these "general" threads. Same goes for the intake/exhaust threads, just post stuff in you respective models thread, you will have a much better chance of finding out what you are after.

Good luck, Matt.