Jay Honeck wrote:

He re-gapped them, and I reinstalled them. They were off, according to my
A&P, so I believe my next step will be to re-gap ALL the spark plugs.

disclaimer: I'm no mechanic, but I've cleaned and gapped a few spark plugs in my
life, both automotive and aircraft.

It's possible you just got a piece-o-junk in the gap and it was dislodged when
the plug was removed, and it will be just fine forever onward.

You could also have an invisible crack in the insulator that only shows up when
hot or under combustion chamber pressure, in which case the problem will reappear.

Some people intentionally make the gap wider than spec, particularly on a plug
that has a tendency to foul.

My understanding of the rationale is that the wider gap gives a more reliable
spark, but causes higher voltages in the high tension wiring, which might cause
other symptons, like crossfiring. Apparently you can routinely get away with a
gap that's wider than spec.

Dave