Cracking a spark plug

[BRXLT]

I have a 2000 Ranger 4.0 and my spark plug on cylinder 5 keeps cracking and of course the porcelain keeps falling into my cylinder when it happens. anybody know why this might happen?

 

[F150hybred]

Crappy fuel would be the first place to start. Inferior fuel will cause a detonation situation that will have many symptoms... one of them is a broken spark plug porcelain.

 

[BRXLT]

well I know my fuel is fresh normally get it at the shell gas station. It's only on cylinder 5 idk what it could be but I only have basic repair skills

 

[LIMA BEAN]

If its lean say due to an injector or signal that cyl. is going to get hot hot. Even if you dont have a CEL on have you scanned it for codes? What plugs are you using? all the cool crap sucks use motocraft.