During my sputter/smoke escapades, it randomly happened when the engine was
warm.  After a long time of trying everything else, a guy with a PC in his shop
pinpointed which ground was bad.  Yep, the invisible one on the left head.

Weird thing about bad electrical connections -- they come and go under the
strangest conditions.  My ground made enough contact on a cold engine to work,
but as it warmed up something expanded or moved, or some chemical property
changed, then no juice would flow.

I'll bet something inside the engine bay is getting wet under the
high-pressure spray and shorting out (is your ECU in the rear pillar?), or maybe the
water is cooling off a connector and causing it to contract away from the
connection.

Obviously, the only thing to do is take apart every single connection and
terminal on/in the van, clean it, and coat it with dielectric grease before
cranking it down tight.  Then test with a quality voltmeter.  That should only take
a month or two. ;-)

Bill Marshall
85 GL Tiico "Pandora's Box"
Aurora, IL