While driving at light throttle I heard a loud pop and the car lost power. After checking everything I found the number 4 plug had blown out of the head. The threads on the plug looked good and so I put it back in but in 25 miles it came out again. So I am sure the threads in the head are stripped. Anyone else ever have this happen?

hello, and welcome. I have had a similar problem with an older vehicle, it was an 85' pontiac Grand Am 4 banger. However the ceramic plug insert came out and the threaded metal end stayed in the head. That thing took me to 363,000 miles. If you're plug is intact and it came out of the head, whole, then I would say that you my friend , have a problem. However, you said the number 4 plug, what engine do you have?? 4- or 6cylinder? It is possible to maybe tap the head ( you would need to most likely remove the valve cover first for easier access) with a slightly oversized tap. If you're going this route I would suggest that you first tap out the spark plug hole with the same size thread first. Then install a new spark plug carefully into the hole. I'm hoping that you don't have the bad plug on the inside bank (closest to the firewall) of the v6. That requires a whole lot more work and nasty words. good luck, there's plenty of help here if you need it.
Jim

Not too hard to do even if its the firewall side plug, get a heli coil kit with the tap and inserts and follow the instructions...

Start the tap by hand with the existing threads on the head before you start using a ratchet

No need to remove the valve covers, just make sure to vaccuum out all the metal shavings after taping it...

hey thanks, didn't think about that. Just wasn't sure if you did or didn't need to pull the covers. I thankfully haven't had that problem yet. Hopefully it's on the RH bank.

Ok great I just checked and the back bank should be just as easy to get to as the front. They go straight down so no hard angles to deal with, on my way to autozone to get the kit. Thanks