clancy

My 2000 A6 2.7 just began to misfire on cylinder 6 at idle. DTC 16690 P0306 -35-00 Using VCDS I can see the misfire count increase on only this one cylinder and only at idle. If I accelerate to 1000-1200 rpms then it clears up and shows 0 misfires.

Is this a coil issue? or ??

Any suggestions?

There was also a store for cylinder 3 misfire, but once I cleared it and idled the engine it did not recur.

16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 -
16690 - Cylinder 6
P0306 - 35-00 - Misfire Detected
16687 - Cylinder 3
P0303 - 35-00 - Misfire Detected

jcman

How old are the plugs and the coil packs?

clancy

bought the car 2 years ago from an audi tech. he fixed anything that had issues but not likely things that did not require replacing. was his wife's daily driver and he wanted it reliable but not perfect. been good with almost no issues. no history on the parts. assume the plugs are not original but don't know for sure. assume the coils are originals. 175000 miles yeah I know, just replace. but hate to throw parts at it if I am not sure of the reason.

GTA_Driver

Swap coils with another cylinder and see if the misfire moves

Also won't hurt to check the condition of the plugs while you're at it.

clancy

will try this tomorrow and report back thanks

jcman

New plugs are cheap and that's a good start first considering worn gaps taxi the coils.

clancy

Pulled the plug to find the electrode gone. Replaced all plugs and back in business.

clancy

note the missing electrode

jcman

At this point Clancy I'd be wondering where the tip is, might be worth it to pull the new plug and scope out the bottom of the piston if you can and use a shop vac with a smaller polyvinyl hose to suck it out or a mag-tipped flex probe.

Good find though!

SloopJohnB@mac.com

OWEEEE…that looks like a detonation/melted ground electrode. Wonder what kind of gas burning? I've not seen a center electrode just…gone…and the ceramic insulator still there. Melted/burned, yes. Given that it's a 2.7T IIRC that electrode is probably long gone and dinged the turbo blades...