Popping plug wires?!

[Kijutsu]

Approximately 10K miles ago I changed all the plugs on my truck. A couple of weeks later, it was misfiring because of bad wires (They looked good at the time, so I didn't change them.) Wires replaced with Motorcraft wires. I used Motorcraft finewire plugs, and for some unknown reason, plug wire #7 keeps popping off! I had to put it on 4 times TODAY. On the way to work it starting misfiring, so I was nice to it, got it to work, heard cylinder 7 tapping away so I hopped up on top of the motor and shoved that little bugger back on and it worked fine.. For about 15 miles. Then it did it again. Dropped my friend off after work, plugged it back in again, and 6 miles later it started going off again. What gives? Why does this thing keep popping off? Plug boot looks good, it feels good and tight when it clicks on (it clicks on twice...) The plug is seated, i dunno why it keeps popping... any advice?

[n5926g]

Swap plug #7 with another one..see if the problem follows the plug.If it does,you either have a physically defective plug,or perhaps the "innards" have an issue letting engine compression slip past the porcelain,and literally blow the wire off.....In my 53 years on this earth..I have seen it happen twice.....

[zman764]

Just pop it back on take a pair of pliers and and squeeze it on super tight.