95 pathfinder-runs rough when warm

I have replaced the distributor, rotor, plugs, wires, air filter, fuel filter, ignition coil. It runs great until it is warmed up, then she run terribly. Most of the time if I run it too long rough, like 2 minutes it chars the rotor, so I use emery cloth, let her cool right down and shell run fine again for 20 minutes or so. Could this be the O2 sensor? Or what? Im at a loss.