Had a similar deal on my Chevy pickup (HEI) last year.
Just putting along, then a couple misses, then a few LOUD backfires through the exhaust, then cleared up.
Drove it 5 miles home and started looking it over.
Rotor had exploded at the center contact.
How the thing cleared up & made it home is beyond my understanding.
Replaced cap & rotor - and 2 pooched mufflers - and it's been fine since.