M42 spits out plug?

[HighschoolE30]

Anybody else had this happen? Was casually driving and my M42 decided it didnt need the plug for cylinder 2. What would cause? Just rattle loose?

[immajackuup]

you didn't tighten down enough or strip thread.

[Roysneon]

Yeah, it could have rattled loose, or the threads going into the cylinder head are stripped and you either need to heli-coil it or replace the head...Same thing happened to me with a non BMW car, had someone else put a heli coil in the head, worked out fine.