i have a 94 4.0 ranger and it misfires when im at highway speeds i have to stay in 4th gear to keep it at 50 to 60 mph the spark plugs on the passenger side of the engine are black and the other side on the driver side the spark plugs are white it misfired when i got it real bad i changed wires and plugs worked great about 2 months later i was driving and the engine started shaking real bad and bogging down and i had to drop to fourth to maintain speed also if i have the throtle wide open it dosent misfire as bad if at all the truck has always had prblems with fuel and the sending unit on the fuel pump is broke and idk if that is a sign i have a weak fuel pump or what and all this started happining when it started to get cold and i noticed it when it would idle it seemed to misfire and drop to 500 to 600 rpms and shake real bad

 

My 94 acted similarly and it was the camshaft position sensor. Mine is a California model so I have a CMP sensor. If yours isn't CA, you won't have that sensor, but your Crankshaft Position Sensor would take over the fuel timing function. Good luck.

 

where did ya find a camshaft sensor?

 

There are two guys who periodically sell them on eBay. I bought mine from them. The quality was OEM and the parts were virtually new. I picked up a couple of them. I didn't realize this post was so old, so you probably fixed your problem. Was it the CMP sensor? Did you even have one on your truck? Thanks, SS