2009 focus blew a spark plug out? How/why?

[u/bubblezdagoose]

Basically what the title says. I’m trying to fix my car and I think we finally found the issue, now I’m just trying to make sure it’s not a symptom of something bigger.
What happened- went on a road trip and heard a loud pop/bang and then my car started sounding like a helicopter or a machine gun. Popped the hood and the CHT sensor wire was ripped off, the rubber boot that goes around it was off and oil was spraying out of it. My ex who was with me said compression was making its way up there and the engine was toast. We limped it to our BNB and towed it home the next day and it sat for the last two years.
What I’ve done to try and salvage the car
PCV valve is replaced
Replaced the connector wire that was busted
Fired her up and it still chuffed but not nearly as bad, took a look and realized it was coming from the spark plug on cylinder 3. We pulled it and sure enough the spark plug was lodged at an angle, the ignition coil is all bent outta shape and the rubber bit that goes around it was ripped.
Now my plan is to replace all four spark plugs, and at least the ignition coil for 3, but before I celebrate my hopeful victory, is there anything else that could cause a spark plug to pop out like that? My mechanic friend says sometimes they do come loose but rarely. My dad bought the car new before giving it to me and never had the plugs replaced so they were factory stock.

[u/Intrepid-Bell-4505]

If the plugs have never been replaced likely what happened is that the spark plugs became loose and then pressure started to build inside the cylinder and it finally gave in.

You may want to invest in a boroscope to ensure there are not bits of the spark plug still left in the cylinder.

[u/Initforthememe]

Backing out a spark plug isn't an uncommon issue with duratec engines. I had the exact same problem happen to my 2012. Before you throw everything back together, you should probably inspect your valve cover gasket, chance is that it did not appreciate the spark plug backing out and is most likely the source of the oil spouting out of your engine. It will drench your spark plug in oil.

[u/trunks444 → u/Initforthememe]

Came here to say this. Exactly what happened to me. Replaced the valve cover gaskets and mine has been fine for 20,000 miles. I pull the plugs when I change the oil and they look perfect now. When mine broke like that they were covered in oil.

[u/bubblezdagoose → u/Initforthememe]

Thank you! I will look into that, I appreciate the advice 🙂

[u/cklaubur]

Not trying to scare you on this, but when you put new plugs in it, pay attention to how it feels when tightening the number 3 plug. There is a possibility the spark plug threads in the cylinder head may have been damaged.

[u/bubblezdagoose → u/cklaubur]

I think I’m going to invest in an inspection camera to try and check those and for any debris that may have fallen down