Nope.

I figured it out a little bit ago.  It is always useful to work on a car's
electrical system at night, so you can see sparks.

I had a bad spot on one of the plug wires.  Why it would only kick in after
the engine was hot, I don't know - I'd imagine something to do with
temperature and electrical resistance - David B. will eventually tell me,
I'm sure.

Thanks for the attempt.

Karl Wolz