My 85 westy (automatic trans) always runs a little rough when cold,
especially at idle.

Today I spray cleaned the engine compartment.   I didn't use a ton of
water, and I was careful not to blast the sprayer at any electronics,
but nevertheless, after the wash, it sounded like it was running on 2
cylinders.  I wiggled the spark plug wires but didn't hear anything
obvious.  After about 15 minutes of driving (and stalling), it
recovered and ran fine all the way home.

Now I'm wondering if the rough running when cold / idle could be an
off & on electrical problem that was made worse by the water?  Any
suggestions about how to diagnose this?

I live in SoCal so I've never driven the van in the rain, but I'm
worried that a big puddle could cause this again.