Re: 1989 Audi 90 Q Idle hunting2

[Steve Manning <stephenm@ix.netcom.com>]

At 01:01 PM 6/15/98 -0400, you wrote:
>Good morning Audi fans.
>
>I still have a slight problem with my 1989 Audi 90 Q.  I cleaned out the idle
>stabilizer as was suggested, only now it will not idle when the engine is
cold, and if I
>turn the air conditioner on, it will drag the revs down to about 500 --
600 RPM,
>instead of the revs going up to compensate for the additional load of the air
>conditioner.   Since an idle stabilizer cost so much, I hate rush in and
replace it
>without being sure it is bad.  
>
>A friend has suggested that may be the brain box (electronic control Module
>(ECM)) thinks there is a short in the system and I need to disconnect the ECM
>and reconnect it.  Does this make sense??  if it does, were is the ECM
located on
>this model??   

It sounds like the idle stabilizer system is non-functional for some reason:
- ISV not getting current (check w/voltmeter)
- ISV not connecting w/ECM (check wiring between ISV & ECM w/ohmmeter; ECM
located in passenger kick panel)
- intake vacuum leak (check both hoses connected to ISV for their *full*
length; check for other vacuum leaks)
- ISV is still clogged up (sometimes it takes more than one cleaning)

Have you checked the codes?  They may give useful information.

Disconnect ISV while running....does it make a difference?  If no change,
problem may be elsewhere, or ISV just isn't getting current.

Disconnect idle/full throttle switch while running....does it make a
difference?  If so, the idle and/or full throttle switch are screwed up and
sending wrong signal to ECM which can cause loping idle.  Replace.

You need a Bentley manual for your car if you don't have one....get
it!..............SLM

Steve Manning:  stephenm@ix.netcom.com
...Physical home: Metro D.C. area, USA
.....Virtual home:  http://www.stationwagon.com