On my 97 f150 5.4, if i didnt use motorcraft or msd coils, they wouldnt last but about 15k-20k miles before they would start acting up. It would start off as an occasional.misfire at idle that would get worse till the coil went completely out. Msd and motorcraft couls would last from 50k-65k before they would start having problems. Money well spent to buy msd or motorcraft coils. Around $280 for the set of 8 msd blaster coil packs. I never ran the msd street fire coil packs, so i cant attest to them. They are about $30 a set cheaper. Those and autolite double platinum or ngk iridium ix plugs have given me the longest service life. Truck shows 303k on the clock, and the clock quit working over 10 years ago. Probably closer to 425k now. Only reason im not driving it now is it has a bad head gasket and needs front end rebuilt. But the old green machine still cranks and moves. I really wish the 4.0 sohc was a v6 version of the 5.4/4.6...kinda like the 4.3 vortech is basic a 350 sbc minus the 2 rear cylinders. Atleast on the 5.4/4.6, you can replace the entire timing system without pulling the engine!
