engine speed and AT

[Kent McLean]

Snoopy wrote:
> Hi. Does my car have any kind of engine speed increase/regulation,
> when the car is not moving, transmission is in "D", and brakes are applied?
> 
> Recently I noticed a very slight engine "shake" under conditions
> mentioned above. It can be increased for example by pushing window
> button, then engine visibly drops ~100rpm and starts shaking like it
> was working on 4 cylinders. Normal idle (transmission in P or N) is
> fine.

Not that I'm aware of. The engine does have various sensors, to adjust
the idle. But "normally" the idle should be steady.

My guess -- an oxygen sensor. If it goes bad, the idle will "hunt",
slowly rising and lowering, not quite steady.  If you hit the window
switch, the electrical load of the window motor puts a load on the
alternator, which slows the engine since the O2 sensor is dying.
Again, just a guess.

-- 
Kent McLean
'99 A4 Avant, V6 Tiptronic
'91 200 TQA #3, with mods
gone: '91 200 TQA x2, '94 100 S Avant, '89 200 TQ