I assume you mean the tip of the plug. IF so, one possibility is the rings are worn or broken. Another possibility is the valves are bad. May be other possibilities.

95 Contour Zetec, ATX (wrecked, sitting in the barn) 95 Mystique Zetec, MTX 2000 Taurus SEL 3.0L Duratec 1994 Crown Victoria LX 4.6 V8 1993 Chevy Silverado 4.3 V6