BrockSamson

I've got a misfire that just started up on my 2.7T.

I got the codes checked at the VW shop in town (no Audi here), and got all cylinders misfiring, with 16684 (random misfire detected) showing up.

After that I ran it a bit more and only got the random misfire code from my borrowed OBD2 reader. I've got the Audi VAG-COM connector on order.

I let the car sit for a few hours and it started up running just fine. Then after about 10 km of driving it starts to misfire. It's fairly weak on the low end, and is obviously lacking power on the high end (3k +) but it seems to smooth out a little.

Today I changed the spark plugs, gapping at 0.032, checked all of my recent work for vacuum leaks, and added some fuel injector cleaner.

I just acquired the car about two months ago, so I'm thinking I'll try changing the fuel filter next.
I put on a new throttle body boot, 710N's, and F-hose just for preventative maintenance.

As far as I know it is a stock 2.7T.

Any ideas?

P0234

If they start after about the car gets warm then chances are it is a lean missfire as the ecu is cutting back fuel once everything is warm. If you had the vagcom you could watch the fuel trims. Anything over 10 spells trouble. Do they occur at idle? Did you do a boost leak test? How did you check for vacuum leaks?

BrockSamson

Lean misfire would make a certain amount of sense to me.

I'm not too sure how long it will be before the vagcom gets here. Probably two weeks or so I'd bet.

It is pretty rough at idle, shaking the car. It's worse at 2-3k rpm with slight amounts of throttle.

I did some vacuum testing using the starter fluid technique. I didn't find any issues there.

Today I checked the OBD2 tester again to see the code for cylinder number 2 misfire, only that one.
-I swapped the coils from 2 to 3 and 3 to 2, and then drove around for the CEL to come on, still low on power and slightly stumbly at idle. The CEL came on and showed cylinder number two again.
-I swapped on a known good spark plug to number two, it didn't change a thing and i drove around for a few but the CEL has yet to come on.

Maybe a bad injector?

BrockSamson

I saw someone else have an issue with a single misfire and it was fixed with the POS. I did the POS swap and watched on the OBD2 reader as it became cylinder 5 that was misfiring.

I'll get a new POS and report back.

Peter Badore

When I had the same problem I bought two new ignition control modules (aka POS) aftermarket, not Bosch, had to file the base plates a little to fit, coated the bases in dielectric grease to aid heat transfer and they have been good for more than a year in heavy high heat stop and go traffic. I also fixed a 2.7l biturbo with the POS from a 160,000
mile 92 Audi 100S 2.8l V6 with only one screw attaching the unit but it has worked OK. A low cost "getto"
temporary repair on a weekend.