2001 Navigator 5.4L - I had to replace one of the coils on the driver's side some time ago, and since then, I keep getting moisture under the coil cover that eventually causes a misfire. If I remove the cover and let things dry out, then the misfire goes away.

I don't drive this truck much. Where is this moisture coming from? Is it getting under the cover from outside, or is something leaking/cracked/broken internally?

 

Could be leaking intake, you did not say which cylinder or what color moisture.

 

Was cylinder #5 this time around. Will drive it for a few days while waiting for F250 6.0L parts and see if/when it happens again and try to see if it's coolant or just water.

Leaking intake? Broken/cracked or a gasket issue?

 

OK, it is up front so it should not be water leaking down from the windshield wiper cowl.

Check color and greasiness.

Could be either reason you mentioned about intake or a porous head casting.

Don't let it take out the coil drivers in the ECU. Factory manifold replacements only if cracked.

 

Thanks for the tips, jesse! reps sent.

 

You probably do not wash the engine or drive through enough water for the fan to spray it onto the engine do you?

If you had previous trouble around number 3 or 4 cylinders the coolant pipe or hose for the heater sometimes leaks.