67,000 miles and all services per the manual, including the 60K. The problem has been going on for 8 months and defys diagnosis. Code "cylinder miss fire for all cylinders" initially and no codes until yesterday. The problem keeps going away, but comes back about once a month.

Whenever I let up on the gas there is kind of a hesitation in the engine. Sometimes it is more noticable than others. It also shows up most noticably on long down grades such as headed south on RT81 in PA.

Yesterday at idle it started searching. The RPMs went from the normal steady 950 to a range from 600 to 1200 and kept this rough idle until we hit the gas again.

Any ideas would be appreciated. I have had it to an Indie and the dealer with no good suggestions. The dealer recommended new plugs and wires, rotor, etc, which were all done at the 60K service. All ideas are welcome, especially ideas on how to diagnose this phantom problem.