I have a 2003 F-250 5.4 and recently it just starting mis-Firing. I basically have a dead hole in onecylinder. However, there is no warning lights coming on in the dash so a basic scan will not tell me anything.It could be various things. plug, injector, coil, cam sensor, does anybody have any recommendations in where to start digging first?

 

Does it do it when idling?If so, you can start by unhooking onecoil packat a time. If you have a bad plug/coil the bad on will show no change while good ones will cause the engine to run rough.

 

Yes, it does mis-fire when idling. I think that is where I will start, Thanks!

 

Checked coils, got lucky first one on the right easiest one to get to. pulled off coil and pulled plug, noticed a little moisture. Changed plug, working great now!

 

Yep...Had that happen on my 00 Taurus. Applied dielectrical grease to the plug and aroung where the boot seats to the valve cover. No problems in the past 3 years...