mc_hotmail

After buying my 2007 A4 2.0T quattro sedan @62,892 miles, I replaced both engine mounts (x2), trany mounts (x2), turbo diverter valve (DV), PCR valve, canister purge valve (N80), center muffler. Except for the muffler, most of these changes were in an attempt to ease the vibration when I shift from P/N to either Drive or Reverse. No success so far.

Today, with the help of my brother, we observed this: when it's shifted to D or R, the engine actually sinks quite a bit in the engine bay (compressing the mounts). When it's shifted back to N or P, the engine raises back to its idle height (same height when it's not running).

My brother's thoughts were that the engine couldn't adjust to the load by adjusting fuel mixture, or the trany has some problem.

Here are some matching symptoms:

1) Idle in neutral, rev the engine, no vibration.
2) Start the go down hill without stepping on the gas, the same vibration will disappear.
3) Cruising on freeway, I don't feel that kind of vibration.
4) Accelerating in low speed, the vibration is still there.

The vibe is not serious, but just annoys me. The growling sound during low speed acceleration also bugs me, but that's a different topic.

Any speculations?

Thanks

Kris Hansen

I recently bought a B7 A4 with the 2.0T as well, and have done a huge amount of research on this exact problem. IT turns out that the torque converter that is fitted to these cars is the same one that al of the other cars in the line use, including the S4.. At idle, the torque converter actually puts quite a bit of load on the engine, making an already less than smooth engine that much worse.

The only real fix for this that I've found is to use a VAG COM to adapt the idle speed up a bit.

Engine warmed up at idle
select engine
select adaption
select channel 01
and enter a value from 124 to 132 (132 being highest)
then save.
Idle will immediatly rise.

This significantly improved the situation for me... it also seems to be better when the temps are warmer..

mc_hotmail

To test Kris' theory, I have 3 more observations:

5) After a cold start, the RPM is about 1,200. Shift to R, and some vibration was felt.
6) Shift back to P and wait till it drops back to normal idle at about 800 RPM. Shift to R. The vibration is more pronounced and is what I normally felt.
7) Still in R, put left foot on the brake and right foot gently step on the gas to increase RPM to close to 1000 RPM. The vibration is reduced and felt like when it was cold.

Therefore, it is confirmed that higher idle speed can ease the vibration.

Kris Hansen

Not only CAN it, it DOES.