Do a good tune-up, plugs,wires, cap and rotor. This should eliminate any electrical problems. If that doesn't do it, swap your injectors from cylinder to cylinder and see if the problem moves with the swap. ( I don't think this model had throttle body injection). If that doesn't do it, run a compression check, all your cylinders should run about the same. If 3 &4 are low, then suspect blown head gasket or burned valves......If you do have throttle body injection, check for vacuum leaks on that end of the manifold....
