I have a 2000 F150 XLT 4X4 with the 5.4 Triton. The thing has a constant miss on cyl #3. I have changed coils and plugs and it will be fine for about 20 miles and start missing again. Lately when I pull the coil, it is covered in rust. I'm thinking it's the intake gasket or cracked head. Anybody have any other ideas?

 

Ok, more info. Also changed MAF sensor, and the only code shows misfire cyl 3.

 

Check the coil wiring. Maybe the injector is messed up? No se.

 

Did you use Motorcraft parts ?

 

I did not use Motorcraft parts, but I did use Autolite plugs.

 

If you have a misfire, something is missing from fuel, spark or compression. Without knowing how many miles are on the engine and you not having checked compression…you get where this is going.

 

or we have coolant getting in the combustipn chamber.
diagnose it & quality parts....