Peter Badore

I have a problem with a 99 A6Q 30V 2.8l V6 AHA code with 190,000 miles. The right bank cylinders 1 2 and 3 misfire severely at below about 1600 rpm with the car not driving. Using VCDS the measuring blocks 015 and 016 will show cyl 1 with 139 misfires, cyl 2 with 68 misfires and cyl 3 with 91 misfires, cyls 4,5 and 6 have 0 misfires before the misfire counter resets to zero to start over. The misfires occur at idle and to up about 1600 rpm. If the engine rpm is held above 1600 there are no misfires or at most 1 or 2. During the misfires the right bank O2 sensor is trying to lean out the A/F ratio with adjustments of of almost -20%. My question is this: Has anyone had an intake camshaft timing adjuster malfunction that caused low speed cylinder bank 1 misfirings in all three cylinders? This A6Q has excellent compression of 175 lbs in each cylinder of bank 1. Other parts already replaced include spark plugs, coil pack, MAF sensor, fuel injectors for cylinder 1 and 4. The timing belt system was replaced about 10 months ago. Also, the camshaft adjuster malfunction DTCs nos. 17930 and 17927 were set once but have not reoccurred in many subsequent scans.

4Driver4

Could be misfiring because it is lean. Is the O2 OK?

Peter Badore

When the rpm is 1600 rpm and higher the bank 1 O2 readings are normal. At idle and up to about 1600 rpm the O2 readings are all minus and up -20%. Also, sometimes the O2 sensors will be shut off (engine in open loop) due I think too many misfires. I just found the identical problems on VW Vortex for Passats with 30V 2.8l V6 engines. Failures of the cam tensioner/adjuster caused similar complete bank misfires. Will take the engine apart soon.

rickat999

my 2000 a6 with the 2.8l motor has about the same problem,misfires cly1,2,3 found out the misses put low octaine fuel in it,ran all that stuff out of it and put 92 in it,cleared the codes,will check in a few days to see if the codes return,the motor does run great! no complaints!

4Driver4

Are the variable intake runners working?

Peter Badore

Yes as best I can tell from scans and activation of the IMT solenoid valve. The bank 1 tensioner lower pad is broken into numerous pieces and the adjuster is jammed in the up position as best I can tell which explains a very noisy engine at idle and the constant low speed misfiring in bank 1.

4Driver4

Nice find. Interesting that there were no complaints on cam out of range.

Peter Badore

I think that the camshaft adjuster malfunction DTCs 17930 and 17927 have parameters needed to set a fault code that include both rpm and engine load. I think that the load parameter is above 70 to 80 percent which would explain why running the engine in a shop or with short parking lot drives would not reset these DTCs after they were initially deleted. It would be nice if VW/Audi would provide complete descriptions of the conditions necessary to set their corporate fault codes.

igozoom97a4

Any update on this?

I have bank 1 misfiring at Idle but once we bring it up above 1000 RPM's the misfires go away. No other codes that we are aware of (however, the problem dates to previous owner and I did talk to his shop and they don't *remember* any camshaft adjuster malfunction codes.

My A6A 2.8 has a ton of miles (187k) and it was noticed as we were trying to diagnose this that the car has an aftermarket head. Not sure about that...

But we did check the timing belt timing (ok) and the CPS. The previous shop has records of swapping plugs and coilpacks and plug wires with no moving of the misfires to the other side.

Your issue sounds as close to mine as anyone's. Like yourself, I kind of suspect that it could be the camshaft chain tensioner, because one of the techs said that he did hear some noise coming from there. But like yourself, no codes that would give a greater degree of certainty before doing a very expensive part swap.

thepope

ignition control module?