The 2004 is the only year where the spark plug threads have 7 threads in the head for each plug. All the previous years only had 3 threads holding the plug in. I had a 04 and a 01 and the 01 blew one of the plugs out when I got on the engine. Had to have the thread retapped which cost me $1500. Of course ford recalled this and corrected it. I sold my 01 after that happening. Bought my 04 in 04
