JForeman

I have a 04 F150 FX4 with the 5.4 3 valve. In cold weather it has a very rough misfire and rough idle at start up and while the engine is cold. When the engine gets back up to normal operating temperature the misfire clears up and the truck runs fine. the cel comes on and flashes revealing a misfire. The only code that shows on the computer is a P0304, Random Cyl 4 misfire. I have change the spark plugs, all coil packs, ambient air temperature sensor,and cleaned the throttle body to no avail. Any tips to help me fix this problem???