I had a #8 cylinder misfire problem on 96 PI, with the spark plug out, I found the gap between the spark plug tip is no more there and those two just connected without any gap--no wonder there is a misfire there. Pull out the #8 fuel injector, the bottom plastic cap is gone too. The cylinder wall is normal, no coolant, or oil, their trace, but just regular brown.

What can cause the spark plug end to bend down to the tip? I am taking out the head to change gasket(#1 misfire with coolant trace in #1 cylinder, and coolant mix with oil) , what should I look check for this #8 cylinder to make sure no other problem there?