i have a 03 expedition with 5.4 and it has 7 codes including #6,7,8 miss fire running to rich and running to lean. i hae change the plugs 3 weeks ago whne it did it the first time . at that time only 3 6 was miss firing so i changes the cop it took care of it and 3 weeks later it is back open for any help

 

Make sure that the springs that attachfrom the coil packthe top of the plugs are positioned properly. They are apain in the *** to get on straight and if there not perfect theyll miss every time.
Good luck, Alistair