My '99 4.6 with 59,000 developed a miss. It was very noticable but never made check engine light come on. I figured I would try wires first, bought Ford Motorsports 9MM and still had the miss. While installing the wires, i must have knocked the heater hose a little loose and it developed a leak, got #3 and #4 wet, figured plugs next step. Installed Autolite Double Plats today and the miss is gone under normal driving but under hard acceleration over 3000 rpms, it starts missing and cutting out. The gap had opened up on all plugs but the only one that looked really bad was #1, it had a lot of carbon build up. I also replaced the fuel filter last week. What's next to get rid of the miss at WOT.

 

weird that you don't get a cel when it misses. I know there has been several threads about heater hoses leaking onto #3,4 and causing coil packs to go bad. Wires and plugs improved it a lot but it seem thatyou still don't get past a high demand situation. I know that there must be a thread someplace about coil pack resistance. I would try looking up a value for the coil resistance and see if the coil is O.K.

 

Yeah if your coil packs are weak they aren't going to give the juice you need at WOT but will be o.k. around town....

 

well, it turned out to be the coil pack on passanger side. put on a new Borg Warner coil (lifetime warranty) and runs great. Pulls through entire rpm range and doesn't miss a beat.