99F150,

The problem you have sounds EXACTLY like the one I have. '94 4.0L/5spd. When I start the truck in the morning and take off for work it will drive wonderfully. Then, after about 10 miles or whenever it feels like it, it will run horribly. Feels like it is running on 1 cyl LOL. Even on level highway, 55mph, 5th or 4th gear, it will just start dropping speed. Almost like you flipped a switch to cut the power. Then if you ride it out it will eventually pick back up speed, like you flipped the switch to turn the power back on.

Came to find out that the plug wires were not snapping in all the way on the coil pack. I replaced the plugs and wires and the problem went away for about a week. Now its back with a vengence. Seems to do it more often. I am suspecting a coil pack as well.

To check the secondary resistence on the coil pack: Remove the plug wires from one cylinder and its pair (1&4 for example) and set your multimeter to ohms. Place a lead in each coil and note the reading. Compare against the specs. I don't know the 4 cyl engines, so can't help you with the specs or which cylinders are paired. Also, it may help to do the readings when the coil pack is cold and after the engine has been running. I would caution about any residual voltage left after the engine is shut down.


Let us know what you find out.

 

I broke down and took her in to the doc today, could not get the problem narrowed down. I hope it is nothing serios and will post results.
Thanks Dan

 

#1 fuel injector was bad electrically. Sometimes would fire most times would not. I know what to look for now if one of the other three go bad.

 

Good feedback, so it was a fuel delivery problem, but one not often found, a bad/intermittent injector!!!! good to hear all is now well & your 'on the road again"!!!!!