I have a '99 Neon DOHCand it seems to have anerractic idle.When ideiling, the car seems to speed up and slow down, like stumbling. It smells rich while idling sportatically. I have replaced: all four pistons and rings, gaskets, IAC, coolant temp. sensors, wires and plugs, K&N air filter. I am aware of the previous owner replacing the timing belt and water pump. I have checked the computer codes and am coming upwith nothing. Thus far, my efforts have not seemed to fix the problem.
Any advice on this problem would be greatly appreciated.