Here awhile back, I had a coolant hose burst on my Exploder, after I fixed that, I got the hose out, to wash some of the sticky crap off. I didn't saturate anything, just ran a quick squirt of water (line pressure, no nozzle or sprayer) over the inner fender, passenger side. Just a quick pass by with the hose, like.
After that, the coils went bad, had misfires, made the trans shift wonky, etc. Sprang for OEM coils (RockAuto will be your new best friend here) and now, once installed, no more issues.
The ones that went bad were some generic, 120 dollars for 8, no-name set that I got from a friend who had ordered them for his V8 Explorer (that he sold before ever putting them on)
So while cheap stuff will certainly work, I can assure I didn't get but maybe 15, 20 thousand miles out of them. When I did the first set of coils, (cheapos) I also put new plugs in.
Personal experience, nothing more, nothing less. I'd expect the same for an Expedition, engine wise, EcoBoost versions aside, it's functionally the same engine, 3v V8. There are different part numbers for coil packs between the 4.6 and the 5.4, I'm not sure what the difference is, but still....cheaper stuff just won't last.
