I think I figured it out. I noticed that one plug wire crossed over another, and it would settle down and they would touch. I put a plug wire separator in, and guess what-no more missfires.

My volvo 740 with 290000K has a miss that shows up from time to time. The idle will tend to go a bit higher, and then I might get a hesitation. I installed new plug wires, and it seemed to cure it, but a month later I again had a miss. One was when I was idling, the other when I was going 30 kph, ju...