2001 Neon spark plug tube rising

Bit of an odd one.
I have a 2001 Neon, approx. 160,000km.
Car started was idling a bit rough this morning for about 20 seconds
after startup. I decided to check the plugs. The spark plug tube in
the (I believe) #2 cylinder, had risen up about 1/4 inch above the top
of the valve cover. This resulted in the spark plug wire not making
solid contact with the spark plug.
I checked inside the spark plug hole and did not see anything out of
the ordinary.
After tapping it back down with a mallet, I took if for a 15km drive
(bit of city and highway run).
I checked the tube again, and it had risen a bit, but not the 1/4
inch.

The car is running good, smooth idle after reseated the spark plug
wires.

Has anyone seen this?
Any ideas as to what would cause this?

Mike
mlawrenc(at)gmail.com

 

I believe those tubes are held in close-fit holes in the heads with
"stud and bearing" type Loctite or equivalent. Either the factory
adhesive failed, or someone did some valve train or other work and did
not get that one glued in right.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')