2005 S4 B6 Sedan - Vibration at all RPM with no codes

Looking for some input and help…

Have a Canadian 2005 B6 S4 sedan with 160KM on the motor. The timing job was done 10k ago after tensioner failure. Put back together with all new parts and upgraded to JHM adjusters and RS4 guides. Plugs, coils, injectors o-rings were all done at the same time as well as valley pan gasket and sprayers. The intake manifold was taken apart and fixed as the flap was seized in the open position.

Driving home the engine developed a slight vibration after a pull to 5K. The vibration slowly worsened and luckily I was close to home and parked the car. In the driveway the car has a slight rough idle and vibrates at all rpms like it has a single cylinder misfire. Plugged in the Rosstech VAGCOM cable and found no codes whatsoever!

  • no CIL/MIL, no pending codes
  • no misfires and zero on all miss counters
  • short term fuel trim cycling between 0 and +/- 0.7 and longterm trim at 1.2
  • O2 voltages look good and don’t appear to be lazy


JHM intake manifold spacers & TB coolant bypass
Fast Intentions cat back exhaust & piggie pipes.
That’s it!

What I have done so far:

  • swapped coils with a known good set and replaced the plugs
  • induced vacuum leak, ST & LT values changed to compensate
  • MAF test, hit 276 g/s
  • unplugged just about everything, no change
  • compression test, 150 to 160 across the board
  • Ohm test injectors, all 15 and within spec

What I found so far:

The only anomaly I found surrounds the knock sensor voltages while monitoring blocks 26 and 27. Bank 2 sensors all report .700v when idling and move almost in unison when increasing RPM. Bank 1 sensors are a different story. When at idle they look like this:

Cyl 1 - .468
Cyl 2 - .360
Cyl 3 - .500
Cyl 4 - .500

Increasing the RPM to 2000 results in a large gap between the 1-2 and 3-4

Cyl 1 - 1.4
Cyl 2 - 1.1
Cyl 3 - 1.7
Cyl 4 - 1.7

Watching on the graph there is a very noticeable gap on Bank 1 for cylinders 1 and 2 with 2 always lower than the rest. The only thing I can think of is moving the injectors around to see if the knock values move accordingly. That said there is no commanded timing adjustments shown on 21-24 measuring blocks.

Any help would be greatly appreciated!

It is a manual transmission? If it is then I would bet that the dual mass flywheel is starting to separate.

Great point.

If it is a manual that would be the first thing to stand out.

It is a manual transmission, had not thought about the flywheel being an issue. If it is the flywheel is there any way to confirm it without pulling the transmission?

The reason I ask is there is no change to the vibration at all when the clutch is applied. That said I don’t know enough about how these fail to know if that is common or not when they go.

Thanks for the input!

Took the car in to my local Audi tech and he confirmed the flywheel. Transmission coming out this weekend.


Good for you.

Just get a JHM LW unit. They honestly make the best clutches and their flywheels add a nice bump in motor free power. The driving characteristics are changed for the better and the dredded flywheel rattle with light weight flywheels isn’t something they suffer from. Unless your trying to do something stupid like take off in 4th gear.

Quick update, The old flywheel failed somewhere in the bearing assembly and had a serious side to side wobble between the two sections. Went with the LW flywheel and RS4 clutch / pressure plate combo. Would not have believed it but the car has never driven the way it does now, feels brand new and revs up much faster than before. All in all a worthwhile upgrade!

Def a good upgrade from stock. If you haven’t already get the JHM tune. That really wakes up the car. Much more funz and really overall changes the experience