The spark plug and where it lives are designed to withstand the pressure of compression and combustion, essentially an explosion! If your mystery vehicle [bet its a ford truck] has spit out a spark plug then the culprit lies with stripped, defective threads in the head, Defective plug or a severely cracked cylinder head. Do not attempt to use a Helicoil in the UK or any other country for that matter. You'll need the appropriate repair based on what vehicle / engine this is. A popular product is called Time-sert and you might make a fix with this if it is only bad threads.
Either the thread was damaged or the plug was loose. If the thread in the head is damaged you can get a repairer to fit a new thread. It's called a 'Helicoil' in the UK.
No. Oil pressure won't cause it.
If you get lucky it was just loose and putting a new one in and see if it will tighten up.
Is being stripped the only reason this could happen?
