Idle problems

My '86 Westi has developed the sudden racing idle problem.  I've unplugged
the idle stabilizer and the engine now idles smoothly at 800 rpm but it
chokes with the air conditioning on.  When I plug the idle stabilizer back
in it idles at 1050 rpm for a while and then suddenly races to 2000 to 4000
rpm.  The idle falls to 800 rpm when it is again unplugged.

There have been several reports over the past few months with this same
problem and it seems from the mail that the problem is a sticky idle
stabilizer valve.  Is this correct?  Has anyone had any success cleaning or
repairing these little beasts?  I have tried using penetrating oil and WD40
and while this removes a lot of crud, it doesn't seem to help the problem.
When people have replaced the idle stabilizer valve has this corrected the
problem?

I've looked over the recent mail on this subject and I've not been able to
reach a consensus on whether the cause of the problem is the idle
stabilizer or the ECU.

If you've had this problem, please e-mail me a description of your
experiences  and I will post a summary to the list.

Thanks,
Ed McLean
North Carolina
'86 Westi, 180K