Hello again!

I have a 2001 F250 4x4 with a 5.4 automatic. The other day i was going to work and the truck seemed to have a little studder/buck in it. So i returned home and borrowed the wifes car. When i returned home that evening i went for another run in the truck and noticed the same thing. I proceeded to add a bottle of gas line anti freeze and went on another test drive(really cold here lately). As i test drove the truck this time, i probabley drove it harder than i ever have before. I never noticed anything different( it worked perfect then and still now) but when i got home, the truck seemed to develope a misfire that could only be noticed through the exaust. Made worse by a whole in the muffler. I went to a friends house that had one of those snap-on scanners and he hooked it up . The machine showed a misfire on number two cylinder. So far i've replaced the coil, switched injectors, replaced plugs to no avail. the only thing we noticed during the whole process was that the number two plug was very lean. It was snow white. The couple of others i changes were tan brown. To drive the truck, the miss it not noticable.


Anyone know where to look for this? Ideas of what it may be?

I had a 01 f150 that had a problem with one coil on damp days and when it was a problem, the truck would shake the **** out of you when it got in overdrive.

 

I should have mentioned that the miss is only noticeable at idle. Not while you drive.

 

might do a compression check to make sure you don't have a bad hole.

 

I'm having the same idle like miss with my truck. Do you have a CEL on? Also what's a bad hole?

 

If the miss is only @ idle check for vac. leak.

 

there is a vacumn hose underneath the throttle body. it is a tricky fix. i have seen it several times. on different vehicles. remove your air cleaner and housing. remove the air duct to the intake. reach your fingers underneath the intake. you will feel the hose. it will most likely be collapsed or have a hole. funny most ford dealers stock this stupid little hose. good luck. any questions let me know.

 

There's no cel on. Yes it's only at idle. I will check what you suggested later today and get back to you. What about the white powdery plug and the scanner indicating a miss on the number two cylinder? If i had a bad cylinder(hope i don't)would that scanner indicate a missfire. One more thing. Iwas talking to a very reputablemechanic in my area and he said if it was a valve or something, the cylinder would be rich and the plug would be black because the gas would not be burned.

 

Good point about the lean vs. rich.

I'd check if the injector is being fired by the PCM - with a DVM on AC, hook it to the injector connector and see if you get any voltage there.

Also, you could be coming up against a strategy in the PCM where if it detects enough misfires, it turns off the injector for that cylinder. But, it's a Superduty, so I don't think it would do that, and besides, you'd get a CEL for that I believe.

https://www.ford-trucks.com/forums/5...t-come-on.html

 

If the PCM turns off an injector for that cylinder how do you reprogram the PCM to turn on the injector?