1999 Ford E350 5.4L
3 Answers
Could be PCM putting engine into limp mode, see if there are any codes being set such as from a cam, crank or knock sensor. Can check also trans fluid, low fluid can be letting TC slip. Honestly there's a lot of thing to check over given vehicles age.
After the engine ran good for about 30 minutes, the check engine light came on. 4 and 6 miss fire coils at random and then again 8 and 3 will also come on and off at random. That is the weird part that they come on and off at random Once the engine has warmed up for a bit. When the truck is cool everything works proper and after 30 minutes maybe 40 minutes the engine is warm and it comes across this problem where I loose all the power slowing me down to under 30 miles an hour going uphill.
Usually random multiple misfires are not a good thing, could indicate a problem with the timing chain. A computer diagnostic might indicate if car is going into limp mode when these occur, as that's how the engine's PCM minimizes risk to itself. You could also try a compression test and see if you're losing power from lack of compression. There's no given solution until the problem manifests itself as a hard fault, you're not sure what you're dealing with. An OBD scan tool that can scan live data while you're driving might give you a better indication than just a few fault codes.