The truck start fine after I changed camshaft sensor. Truck has a rough idle and hesitates while driving. After supposedly fixing problem same problem comes back after 4 to 6 months. Done tune ups. Changed crankshaft sensor, camshaft sensor, ignition coil, #4 fuel injector, changed wires and plugs with factory parts 6 months ago and it is acting up again. What is the problem and why does it come back every time. Thank you for your response.