January 27, 2011my 2000 f150 5.4l has had a curious issue happening lately. Engine will run on (I`m guessing here) sometimes 7 or 6 cylinders. The when I last checked the error codes it was for rough idle (I forget the codes, but I have them somewhere). Sometimes it will start up and run real rough then smooth out to all 8 cylinders. Then it can switch back and forth between dropping cylinders and smoothing out.
I was driving it the other night, ran for about an hour straight no problems. Started back up after an hour or so, drove 5 minutes, got on the gas leaving an intersection and then 2 cylinders stopped firing. Kept driving, got let the truck coast on a down-hill and when I got on the gas again at the bottom, all 8 were firing again.
So, what could it be? Fuel? Electrical? I`m leaning towards electrical. Maybe corroded electrical connections on the fuel injectors?
Engine makes no knocking sound or anything out of the ordinary. Just a few cylinders deciding not to fire.