1989 Audi 90 Q Idle hunting

[Anthony Attard <ACA@nrc.gov>]

Good morning Audi fans.

I have a slight problem with my 1989 Audi 90 Q.  When I come to a stop light, the
idle speed returns to where it should be (around 850 rpm), but a couple of seconds
after that, it starts to climb up to a 1000 rpm or higher (as high as 11--1200 rpm). 
Sometime it comes back down to a 1000 rpm and sometime it stays at the higher
revs.  I believe auto technicians call this "idle hunting".  Does anyone have any
suggestions.   Is there a idle stabilizer on this model??  

I am open to any suggestion(s).   Thanks a lot.

Tony .    1983 Audi Q Turbo
               1986  4000 CS Q
               1989 Audi 90 Q