Thought I'd throw this out to the list.  Our 87 westi decided to begin to
Idle at 2000 rpms this weekend.  When you tap on the throttle the idle goes
back to normal for a short time and then climbs back up to 2k.  I searched
the archives and found that the usual suspects for this problem are throttle
switch, O2 Sensor, TempII Sensor, Idle controller, and Idle stabilizer valve.
  The van runs worse with the O2 disconnected.  When I clamp the hose from
the Idle stabilizer valve the idle speed reduces somewhat.  Any clues on the
best way to trouble shoot this problem?  I don't want to just throw parts at
it until the problem goes away... If I did I'd take it to my local European
Auto Specialist :-)
'TIA
'Don Record,
York, PA