Re: Erratic Idling...

[steveb@newkla.kla.com (Steven Buchholz)]

Shannon:

I didn't respond to the original posting because I couldn't think of 
anything to cause your problem.  When I heard you were contemplating 
swapping out the Idle Stabilizer, I wanted to let you know about some 
of the diagnostic features built into the car.  Then I got an idea about 
an insidious source of vacuum leaks that you may have missed.  I don't 
know if the '89 100Q is the same as an '88 5000CSQ, but I had a problem 
where the engine would idle poorly on occasion for no apparent reason, 
and then get better before I could find the problem.  On my car there 
is a crankcase ventilation line that runs from the valve cover down the 
engine on the left side (as viewed from the front of the car).  Where 
the metal line connects to the crankcase there is this large rubber 
piece that connects to the crankcase.  This piece is about 4" long with 
a 2" diameter and is made from very thin walled European rubber (which 
is the very best as we all know!)  This rubber piece had deteriorated 
due to high temperature and exposure to oil vapor, but all of the deter-
ioration was on the side against the engine block!  Maybe you've got 
the same thing.

WRT built-in diagnostics - I have found that Audi has done a very commend-
able job in including user accessible diagnostics in the climate control 
and engine computer.  What's more, the Bentley manual actually describes 
how to use the diagnostics!  I recall from the Bentley manual that there 
is a diagnostic that allows testing of the Idle Stabilizer actuator.  
Read this before you go out to spend all those bucks!  If you don't have 
the manual, send me e-mail directly and I'll copy what I have and fax it 
to you.

Steve Buchholz
s_buchho@kla.com