My '92 eg hatch/vx has been running like shit for a while. it would bog and stutter. then i changed the plugs and wires, properly gapped the plugs. ran ok, then had cel. got a new dizzy/cap/rotor. still ok at best. checked wires, oil on plugs and wires. so i pulled the wires and plugs to replace the valve cover gasket and plug grommets, and noticed that the #4 plug was eaten up. literally. the top of the plug was basically missing the whole top part that sparks, and the ceramic was chipped/melted away. so i'm guessing a bunch of little pieces for FOD (foreign object damage) are in my cylinders. so what happened? how do i fix it? spark plug was destroyed in #4 cylinder. what happened?