Similar problem with my 81, turned out to be the decaration valve.
Plugged the vacuum line until I got  a new one.
Keith

Peter Cassidy wrote:

> >My 88 Wolfsburg GL just got the case of the high
> >RPM's! When I put it into Neutral or Park, it shoots
> >all the way up to 2200rpm, in drive it hovers around
> >1200 RPM.  We tried to clean up the Throttle body,
> >adjust the switch, adjust to idle, and clean the idle
> >stabilizer and nothing works.  The funny thing is it
> >doesn't even appear able to adjust the CO.  I need
> >some ideas if you don't mind about what things to do,
> >look for....etc.  If anyone has a step by step
> >procedure, I'd really appreciate it.
>
> My '88 Wolfie was doing this for a while. Here's what
> happened; when the engine heated up & I was stopped at
> the lights, the idle speed would creep up and up,
> usually to about 1500 RPM but often over 2000. Engine
> braking was minimal & the van started bucking when
> cruising at 40-50MPH.
>
>  - Checked for air leaks around the throttle switch
>    and intake plenum. Nope!
>
>  - Checked all vacuum hoses were not sucking air in.
>    Temporarily disconnected the brake servo lines &
>    plugged the ends. Nope!
>
>  - Cleaned, then swapped out the AFM. Nope!
>
>  - Unplugged the idle stabiliser valve while the engine
>    was idling fast. Woohoo - it dropped like a stone
>    & idled about 800 RPM.
>
>  - Figured it was the idle solenoid. Replaced it with
>    a second-hand one from German Parts Warehaus in
>    Rancho Cordova, CA. Idle got slightly better, but was
>    still bad.
>
>  - Swapped out the replacement solenoid & traded in the
>    new one for a new idle stabiliser unit (the guys at
>    German Parts Warehaus were great!). Problem went away
>    completely!!
>
> The replacement controller cost $120. It is located behind
> the right-hand rear light in a compartment where the intake
> air hose goes. Undo three clips & remove the panel & hose.
> The box is mounted on a 'holder' & can be slipped out ...
>
> Pete C
>
> --
> Peter Cassidy,                   pcassidy@apple.com
> Sr. Test Dev. Engineer             +353-21-284316
> WW Operations
> Apple, Cork, Ireland.