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Spark plug popped out

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Hey all new here, just got this 1996 subaru legacy outback about 5k miles and 4 months ago... Great deal and only work I did so far after oil change was a head gasket sealant liquid to stop a slow leak of radiator fluid, which worked great and haven't had any coolant leak since.

However, just yesterday, as I was driving to work, I heard a loud bang and engine started running rough, shaking and sputtering. Pulled over, got a ride, came back to look and found the spark plug with holder completely loose and i just easily pulled it out to look at it.

What I'm wondering is why the spark plug fell out, no stripping it looks like, and also it looks like it melted around the holder? Do I need to get new spark plug wires as well as new spark plug? Going to try to fix it soon, it's my daily driver for now for my 15 mile commute, but I'm not really able to dump a ton of money into this.

Thanks for the help.



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Looks like it was loose for some time and combustion fire escaped to melt the boot.


My concern is that the threads in the head are ruined because they are made of aluminum so they would fail before the steel plug would show any damage.


You'll have to check out the hole. If the threads are wrecked it is a big deal.


Also, find out the torque spec for the plugs and use a torque wrench to put them in. Lot's of people have destroyed engines by severely over torquing spark plugs.


Good luck with that hole and please keep us posted on your progress.

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I had the exact same thing happen on my 96 2.2L and even the same plug got spit out. You can have it helicoiled (don't attempt on your own) but it's risky and in my case it lasted until I pulled the plug out for the next service and the heli coil came out with the plug. Ended up putting a new (used) head on it.
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To helicoil it is not hard, it's just access that you need. All depends on which plug.

Once you get the kit, you have to turn it by hand. When drilling the hole use axle grease or something similar. This will catch any chips as you cut.

As a precaution you can use a small vacuum hose afterwards.

Follow instructions for setting the correct insert.

Put anti seize on the spark plug before install.

If you have an inch pound torque wrench to use, go for it. Don't know the actual foot pounds Remember 12 in is 1 foot!!!

Have been installing plugs for over 50 years and have never used a torque wrench and never had one leak.


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