Mitsubishi Repair: 97 ECLIPSE SPARK PLUG, eclipse gs, cylinder auto

Question
97 eclipse GS. 4 cylinder auto 85,000 miles
The #1 plug dislodged from the head still housed inside the plug wire.  2nd time this has happened in past few month.  No way it could have worked itself loose.
Is it possilbe the threads are stripped on the head itself and the compression is blowing it out?

Answer
Ron,
The head is aluminum, so stripped threads can happen.  I would recommend a compression test just to be sure it's within tolerance.  I would also try replacing all the spark plugs.  It's possible the spark plug in #1 is was manufacturered with an imperfection that prevents it from holding the threads.  Replacing them all ensures you know its not the plugs.  If you have ever cross-threaded that #1 plug, it could be causing your problem.  But change the plugs first before replacing the the head.  It's definitely a lot cheaper.
Good luck!