re
cold start valves .............??

there isn't one, or any, cold start valves.

very commonly on 1.9 wbxr's ..
people have the timing set too advanced.
that causes a high surging idle rpm.

also need to make sure the throttle swtich makes contact *every* time the
throttle is released.
it's very common that they don't quite achieve 'idle contact' every time.

idle booster ?
oh...perhaps Aux Air Valve .

besides many other things that are often not really up to spec or in tune,
very commonly ..
it's too advanced timing, and throttle switch function.

distributors too ..
I'm finding those with excessive play in the shaft and perhaps they have
'wandering' timing, or irregular timing,
and you havn't mentioned Idler Strabizer which can affect timing and idle.

throttle bodies get warn and tired too.

scott
www.turbovans.com

----- Original Message -----
From: "Mike Riley" <mkriley@FUSE.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, August 17, 2010 4:01 PM
Subject: idle problems

> strange problem with 1985 manual 80,000 miles.
> surging idle,
> throttle body tight and returns to stop every time. switch ok and working.
> all idle booster and cold start valves have the vacuum blocked at the
> manifold<makes no
> difference>.
> vacuum advance seems tight and no leaks.
> car will surge at random to cutoff and continue to do so untill the
> throttle is blipped a random number of times, then it is ok for a while.
> any ideas?  runs great otherwise.
> thanks
> mike