I have a 2007 5.4 and just recently changed all plugs because it was missing. The check engine light was on but could not read the code...machine just kept saying "error" but after i replace the plugs, it ran like new. Bout two weeks later it started doing the same thing. Do i need to replace coil packs or what else might be goin on? please help

p.s. Im really trying not to have to go to dealer if i dont have to

 

I have 02 5.4 had similar problem changed plugs ran fine short time started missing again humid day. Pulled cop replaced all the boots and used lots of dielectric grease before reinstalling. Grease between boot and plug also between boot and head. Since then no more missing 3 months now.