Spark Plug Boot and Spark Plug Problem

MindyMark

Registered
I've got an odd problem on my 1996 Cougar - 4.6 V8. On the drivers side rear cylinder the spark plug boot and the spark plug are coming off on a regular basis. It is getting to the point that the spark plug boot won't stay on for more then a few miles. As for the spark plug it just unscrews itself eventually.

Here is the history and the things I or other people have done to fix it:

150,000 - All new spark plugs and wires put on.

180,000 - The spark plug came out for the first time. I put the plug back in and laughed it up as a fluke.

200,000 - Spark plug came out again but on the interstate this time. As a "get me home effort" I put some blue silicon on the threads to help it stay in.

205,000 - I put on new plug wires to fix a cylinder misfire problem.

212,000 - I sell the car.

Unknown Mileage - Buyer calls to ask if I ever had a problem with the spark plug coming out. I give her the brief history and she takes it to her mechanic. They do all new plugs and put in a helical coil on the trouble cylinder.

217,000 & 2 1/2 years later - I buy the car back but the check engine light is on for a cylinder misfire. This time it is just a loose plug wire on the same cylinder.

218,000 - All new Motorcraft plug wires.

219,300 - The replacement plug has started to work it self loose again as well as the plug wire failing to stay on.
So what would cause a plug to continually unscrew itself (old plug and new plug) and what would cause the plug wire to come off (both old and new plug wires).

Do I have a possessed cylinder that just doesn't want to play nice?
 
Only thing is vibration loosening the plug wire. The plug loosens because the treads are not holding. Once it gets loose enough it jumps up and down thousands of times from the compression, which will loosen the wire.

Put some sort of loctite on the plug, not the red stuff but something mild. If it has a heli coil then it will be OK. Crimp the end of the wire slightly to make sure it connects properly.

Good Luck.
 
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