I had similar intermittent problems with one of my 2.1 vans, eventually found it was the hall sensor in the distributor.

Swapped distributor, problem went away....

YMMV

---------- Original Message ----------------------------------
From:         Trooz <trooz@ROADRUNNER.COM>
Reply-To:     Trooz <trooz@ROADRUNNER.COM>
Date:          Wed, 27 Jan 2010 16:43:16 -0800

>Particulars:  1990 Westy, 217K on original engine.  Today I went out to run
>some errands and the van wouldn't start.  Cranked as usual, but no start.
>It always starts right up, but not this time.  Let it sit, tried again, no
>start.  Let it sit, tried again, and it started.  After several miles I was
>rolling along at about 45-50 mph and it just died.  The tack dropped to
>zero, I lost power, and as suddenly as the power left it came back.  This
>was just a fraction of a second.  A mile or two down the road it did it
>again, but this time for maybe two or three seconds, and as I was pulling to
>the side of the road it came to life again.  Then again about a mile later,
>only this time it was dead.  I put my flashers on, but they didn't work.  I
>tried to start it a couple of times, no go.  I hit the flasher switch a
>couple of times and suddenly they started working, then I tried to start it
>again and it came to life.  Then I had an uneventful drive back home.
>
>Now I'm afraid to try to go anywhere.  I checked the battery terminals for
>loose connections; everything seems fine.  I don't have a clue as to where
>to start looking, and since it's intermittent I'm afraid that a shop
>wouldn't be able to replicate the problem.
>
>I wondered about the ignition switch itself, so when I got home I fussed
>with it some without turning the engine off but no amount of jiggling and
>wiggling the key in the ignition produced anything.
>
>I guess I'll go out and start pulling and re-seating relays, checking and
>cleaning grounds, etc., but other than that I'm clueless as to what it might
>be.  If I remember corectly, I had the usual red leds and could hear the
>fuel pump pressurize as I switched the ignition on each time.
>
>I'm hoping that some of you electrical wizards on the list will recognize
>that symptom and have some feedback for me.
>
>TIA
>
>Bob Trousdale
>'90 Westy
>