My '85 had this same sort of problem this spring. After messing with everything, 
lubing everything, and not finding the cause, I went internal. Yes, my beast is 
starting to suffer from the dreaded�throttle plate / bore wear syndrome. The 
problem got slightly better after driving it for about two days, (after being 
put up for the winter) but the idle is not consistent, and there is still a 
surge at very low throttle settings.Try this. With the engine not running, and 
the throttle held open, try lifting on the throttle shaft at the spring. If it 
moves more than a tiny bit (a couple of thousandths of an inch), you too are 
also suffering from a worn throttle bore. A large part of you problem may be 
coming from there. There could also be a slight coating of crusty crud around 
the throttle plate movement area that is causing extra drag. Carb cleaner will 
deal with this easily.�The throttle plate is dragging on the bottom of the bore, 
and the spring cannot be made strong enough to pull it closed! Unless you LIKE 
garage door springs as return springs...

________________________________
From: Mark <mbrush@GMAIL.COM>
To: vanagon@GERRY.VANAGON.COM
Sent: Wed, July 7, 2010 11:36:03 PM
Subject: engine revving at idle

Has anyone had this problem?� After my engine reaches operating temp and is
in stop and go traffic, it doesn't fall back down to idle after I accelerate
to move forward in traffic.� It just stays revved at 3,000 rpm or
thereabouts.� Not fun when stuck in traffic.� I'm thinking it has something
to do with the spring on the throttle (maybe needs to be cleaned or
greased?).� I haven't worked on this part of the van yet, so I'm not
familiar with how the accelerator cable hooks up and works in the engine
compartment.

Thanks for any insights!

Mark

--
Mark
1990 Westy (2.1 - manual)