For a misfire, you already mentioned the coil, but also look at plugs and wires. Do you know the last time plugs were done? If you end up changing plugs, get the Motorcraft OEM plugs (forgot the part number) or their Autolite equivalents (APP764 for my Duratec).
EDIT: I should say that if you're having enough power loss that it won't shift into 4th, then you either have multiple plugs that are fouled to the point they're not firing, multiple wires that have disintegrated to the point of not firing, or a coil pack that's not working any more. My money is on the coil pack, but keep in mind that plugs are cheap (APP764's were $4 apiece for me) wires are a little more expensive ($60 for the set) and the coil pack is pricey (over $100 IIRC). If you don't mind spending the money on a tune up, try plugs first, then wires. If you end up having to replace the coil pack anyway at least you'll have part of a proper tune up done, too.
Last edited by hetfield; 04/21/03 07:19 PM.
