I OWN A 1999 LINCOLN NAVIGATOR (FORD ENGINE 5.4L DOHC) ONLY 52000 MILES. THE SPARK PLUG #4 BLOW OUT OF THE ENGINE WHILE DRIVING ON THE HIGHWAY. I'VE SEEN MANY OF THE FORD EXPEDIGION AND LINCOLN NAVIGATOR OWNERS EXPERIENCE THIS SAME ISSUE. THERE IS OBVIOUSLY A DEFAULT WITH THERE ENGINE FOR THESE MODELS AND THUS SHOULD BE RECALLED.*AK