Re: s4 rough acceleration

[Marc_Nguyen@mail.amsinc.com]

> I have a 94 s4, bought at 87k,nearing 100k now and seems to have
developed a
> roughness during acceleration. Most noticeable at 3000 to 4500 rpm at
half to full
> throttle in second gear. Less in 1st and 3rd. None in 4th and 5th. Idles
fine, pulls
> strong. More noticeable when cold. One shop couldn't find anything wrong,
another had a
> computer read out of failing engine RPM sensor, which was replaced and
seemed to improve
> it somewhat.  Any suggestions?

A friend has a similar problem with his '92 S4.  If the car sits outside
overnight and ambient temperature is below about 40 deg F, it "bucks" under
moderate to hard acceleration above 3000 rpm.  After about 10 minutes it
runs fine.  If the overnight outside temp is warmer, it runs fine.  We
dumped the error codes and found nothing.  Took it to the dealer and they
couldn't figure it out either.  A local wrench has suggested
testing/checking the coolant temperature sensor.  We'll be checking that
this weekend.  I will post if it is the problem.

BTW, if you dump the error codes with the car off, you will always get the
engine RPM sensor fault (2111, I think).  The Bentley says to ignore it.
The dealer my friend took his car to did just that and replaced the sensor.
They did not charge him for it when we pointed out their mistake.  You
might want to check with the shop and see if that's how they did it.

- Marc

'93 S4
'85 urq