I have a '94 Skylark 4cyl that is driving me insane. It began by losing power from time to time until finally it lost power all together and the coils and housing were replaced as well as the plugs. It began overheating. Nothing I could do would stop that until I finally bled the system at the top of the motor by releasing the clamp while the motor ran and allowing the air to escape like a mechanics wife told me to do. Now I cannot get the car to stop blowing black smoke like a diesel and sputtering . But what is strange is that some days it will try to overheat again and the black smoke will be gone during that time. When the cooling system calms down the black smoke and very rough running, sputtering and annoying power loss returns. I have replaced the coils three times, plugs the same number, coil housing the same number and have repaired a hole in a vacuum hose.I have also replaced the oxygen sensor twice, coolant temp sensor, and crankshaft position sensor. What am I missing? Any suggestions? I am running out of ideas and money on what is otherwise a great little car.Edited by: Bowwow