I have a 1998 Expedition, 5.4L. It is throwing a P0300 random/multiple misfire. What could cause this? It has had the plugs/wires replaced about a year ago, so I dont think it could be that. It also should tell me which cylinder is bad if it were one of those.

I am thinking it is either the distributor (do these cars have one), fuel system, or maybe a sensor or the computer. Could anyone lead me in the right direction on this?

 

There is neither a distributor or spark plug wires on your engine.

Usually, it's bad spark plugs (a lot depends on what brand was used) or bad COPs. Might be an intermittent crank sensor, perhaps a restricted fuel filter.

Based on how your question was posed, it appears likely that you are unfamiliar with this system and are most likely lacking the needed diagnostic tools. Referring the diagnosis to a capable mechanic would be in your best interest unless you are willing to invest time into learning how to diagnose the system and money for acquiring the proper test equipment. If you.re up to it, plent of help is available here.

Steve

 

your truck has one coil per cylinder sounds like one or two coils are going,you mentioned you changed plugs?what kind of plugs did you put in and where they gapped or pregapped?and i really do hope you installed original motorcraft plugs?

 

I Purchased the car with the previous owner (a friend of mine) telling me he had them replaced so I don't know. That is why I didn't know that the truck didn't have a distributor. I have worked on a 4.6 F150, but not one of these.With a 3 month old, I don't have time to mess around with this... I think I'm gonna just take it to a mechanic.

 

basicly the 4.6 does have coils but 2 what i would call 4packs?each of the 4.6 coils controls 4 cyl.bue the 5.4 has one coil per cylinder?now keep in mind previous owner did tune up a year ago but if he was really beating on it it could be tune up time again,and maybe he didnt use the original plugs,so i would change plugs first,while your there check every coils connection,make sure the two wires goin in coil are not broken and that the pigtail is not broken either,take out each coil check the boots,cause if it has a cracked boot that could be the problem?after changin plugs if shes still running bad and the check engine light is still flashig ?you might wanna try to un plug coil by coil while shes running and the coil that you unplug and shes still running the same that could be the bad coil givin u ur nitemare?good luck???