Same thing was happening to mine a week ago. First I did fuel filter. didnt help a thing but it was the original from 200,000 miles ago so it needed to go. Then I did your usual tune up, Plugs, Wires, Cap, and Rotor. Which had helped a little bit but not much, finally decided id throw a whole new distributor at it, and it fixed the problem. so if youve tried everything but that then id say its worth a shot.