Engine miss/backfire '97 Civic EX

Hi guys/gals. I have a problem with my '97 Civic 1.6L . The car has @120,000 miles on it. Every second day or so, it will start missing out of the blue and occasionally backfire. The local dealer has tried a number of things but nothing has fixed the problem. They've re and re'd the distributor and disassembled it thinking something was amiss internally, but they found nothing wrong with it. They replaced the O2 sensors as well. Cap/rotor/wires/plugs are all ok!? Has anyone experienced anything like this? If so, I'd appreciate hearing what some fixes were!! Thanks:banghead:

Are there any other symptoms besides the misfiring? Does the check engine light come on, if so what's the code indicated? Generally backfiring is caused by a very rich fuel mixture or improper timing. Also, have the ignition components been replaced, even though they "look good"?

No there is not a check engine light on!? Only plugs/cap/rotor/wires have been replaced!