Bart,
I've tried everything to solve this on my 84 1.9.
It is probably surging because once it is warmed up it is actually idling to
fast. With the idle switch closed, the computer shuts off the injectors when
the idle gets to high for some reason.  If you idle it down to  about 950
when its warmed up it will probably stop surging. . . but then it won't idle
when its cold.
You can check the cold start valve by pinching off the big hose that goes
between the cold start valve and the manifold when the engine is cold and
the rpms should drop. Then after the engine is warmed up pinch it off again
and the RPMs should not drop.
My latest attempt to fix this was to get a set of rebuilt injectors. Now it
does seem to run better in general, and takes longer before the idle starts
to creep up. We'll see what happens on a nice warm day when I've been on the
road for a while. If it is fixed finally, it will have been the rebuilt
injectors. That was the only thing left to try.
Steven

----- Original Message -----
From: "Bart Holmquist" <barth@UNLSERVE.UNL.EDU>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, April 17, 2008 11:37 AM
Subject: 84 vanagon wasserboxer

> After warming up a few minutes with smooth idling, the idle then
> starts galloping with a cycle of about 3 seconds and an RPM change
> guessed to be from 700 to 1500 or there abouts. On cooling the whole
> cycle can be repeated i.e. smooth idle while cold, gallop when warm.
> When driving (216k) it runs fine with good mileage (22-24 at 55).  No
> apparent other issues: wires OK, coolant OK, plugs OK.  Where should I
> start looking?
>