My 2000 Ford Ranger has a 3.0 V6. The number 4 cylinder is not firing. When I shift into gear (forward or reverse) it feels like it's running on 3 cylinders, the transmission shifts hard and I can barely keep it running. We found a blown 15A fuse that controls the Heated Oxygen Sensor, EGR, Vacuum Regulator, EVR Solenoid, Camshaft Position Sensor (CMP) and the Canister Vent Solenoid. When we replaced it, the truck ran perfect. The fuse kept blowing during test rides and we cannot find the cause. Until we find the cause, I have to pull over and change the fuse when it blows. Can you help?