hey all, new user here-i'm having a prob w/my '98 f-150 that my mechanic (who i trust completely) is stuck on. it's a 4.2 liter V6, 5 speed manual tranny. 130 K miles and living in hot and humid Florida. The problem is the number 5 cylinder misses when the engine gets hot. the check engine lite starts blinking and engine runs very rough. Engine runs fine after cooling off- every time. My mechanic has replaced the plugs, wires and ignition coil with no effect. it's not losing any coolant and there is no sign of water in the oil (head gasket ?) HELP!