mhk1058

OK, had this 2004 B6 3.0 Cabrio for 2 years and it has had an occasional flashing CEL all that time. Now has 95k miles

Basic code reader indicates random multiple misfires and misfires on 4, 5 and 6 (ie one bank only) Rarely just 4 and 6.

The car idles just fine,runs perfectly most of the time, misfires/CEL flashing happen (occasionally) when cruising or pootling around town, never noticed it happen when accelerating hard.

Recently these have got worse with occasionally real hesitation pulling away from lights etc with one occasion when the car became almost impossible to drive, crazy hunting idle, running rough as hell. CEL full on and ESP light on (?), yes the ESP light - I guess this is connected to the ECU's interpretation of engine/wheel speed differences which were all to pot with the misfires.

Managed to limp home, loads of codes, MAF, Lamda, misfires - cleared them and as if by magic, the car ran fine again( but still throwing the occasion random misfires.)

Just to confirm, the car usually idles just fine and runs great (you can just feel the slight stumble prior to the CEL flashing ) Sometimes it will misfire every time you drive it, other times you can drive 100 miles and nothing - it's not something that I can consistently replicate.

Stuff done so far:

New MAF
New coil packs 8 months ago (Audi recall)
Coil pack swap over
Removed coil wiring harness plastic covers for visual check of insulation
New Plugs
New rocker cover gaskets
New PCV valve and hoses where suspect
All vacuum lines checked
Fuel rail lifted and blown through
Injectors cleaned, resistance checked and swapped left to right.


Nothing changed, still exactly the same, occasional random multiple misfires 4, 5 and 6. This is my wife's car and she now won't drive it as she is convinced it will leave her stranded.

Only things left I can think of are:

Timing issue, one tooth out on one bank (unlikely considering random and occasional nature not connected with high revs)
Intake leak or vacuum leak (although car idles nice and smooth apart from the freak out mentioned above)
Exhaust issue (leak, cat, oxygen sensor - no codes for these though)
EGR valve - no codes for this either
Head gasket (but not losing water or oil)
Fuel pump/filter (but why would this only affect one bank)
ECU (please no!)


Not much hair left to pull out but I'm trying! Has to be something related to that side of the engine.

Right, here's a snapshot of my cam timing.

Not really sure what I'm looking for here but common sense says bank 1 and bank 2 should be about the same. Block 093 looks odd to me with quite a difference in correction factor.




Common sense also says that if the cam timing was out wouldn't the misfire be more consistent and have some timing related codes? (happens at various revs/loads and not all the time)

Thoughts welcome before I hand the keys to the next passer by.