Bob, I have had this be caused by:
1. Ignition switch going bad and large amount of keys is actually
shutting the ignition off.
2. ECU is getting flakey.
3. Hall Sender in distributor is getting flakey.
4. Bad wire.

You can check the ECU problem if you have a known good ECU to swap in
and see if it still does it.  You can also buy a new ignition switch for
$9 and just plug it into the harness without installing it to see if
that will stop it from happening.  I have had a wire on the coil that
has a bad end on it cause this problem before.  Try wiggling the wiring
while the van is running to see if you can make it stall.

Just ideas.
If you need anything let me know.

Ken Wilford
John 3:16
www.vanagain.com

Trooz wrote:
> I finally got the big problem fixed; now I have a mildly annoying one.  My
> van will suddenly die at idle occasionally.  It starts back up with no
> problem.  There are no obvious preliminaries indicating that it's getting
> ready to quit, no coughing, no sputtering, it just stops.
>
> I just replaced the spark plugs and the distributor and the temp II sender.
> Other than those items it's basically original with 218,000 miles.
>
> Anyone have an idea as to what might be wrong?
>
> Bob Trousdale
> '90 Westy
>
>