I have a F250LD with a manual and 4.6l. The truck runs good for the most part but I have a weird issue that seems to be becoming more frequent.

It has a weird hesitation that will come and go under all throttle load except cruising. I thought it might be spark plugs and or coils. I was told the plugs were changed about 20k ago, unknown what kind. Although I will say the previous owner was meticulous and I haven't found a non Motorcraft part yet. I have also tested the coil bricks with a multimeter and they check out.

This has also started just in the last 2 weeks
It will also idle up and stays high like a vacuum leak, but it does not do it all the time so I cannot think its vacuum. I did replace the TPS that died on me over the winter, I did not use a Motorcraft part. Sometime I can pop the throttle and it will come down and other times it will hold to what sounds like 2kish (do not have a tac). When acting up it will also drive itself like the cruise control is on when you take your foot off the gas. Its a manual so it should start decelerating immediately.

I have not torn into it much cause its winter and I have no garage, but the weather is getting nicer so I want to start lining up things to check on the next nice day.

My gut is telling me there is a sensor that is giving me trouble, but not enough to trigger a check engine light.

Need some guidance!

 

Sounds like your have a vacuum leak, check the PCV rubber elbow for any signs of cracks or it's collapsing. As for the hesitation could be caused by the vacuum leak, when in doubt do a complete tune up (spark plugs, fuel filter, air filter etc.)
Also when you did the TPS did you adjust it with a n OHM meter to specs? This will also cause it to run like chit. And the TPS are the rarest thing to brake in these engines, just a thought.

 

Vacuum is what is feels like thinking about the symptoms. I might try the cigar method the next day its not raining.

A tune up is on my list to do this summer, as I am not sure about spark plugs that were used and when honestly. I did however do a fuel filter when I bought the truck and the air filter was new when I purchased truck.

I was not aware that there was an adjustment on the TPS. The one I took off does not say Motorcraft any where and the AutoZone one I put on does not look adjustable? I will have to check my book and see if I can find the procedure for this.

I was actually out of town when the TPS went out. It would fire like normal, RPMs would go up like normal and then when it should have come down to normal idle is just went straight to dead. You could keep it running if you held the pedal but the truck idled really hard like it wasn't firing on all cylinders. Ran to Autozone got the TPS installed it and all was normal.

Last night I took off the TPS and intake hose and blew some throttle body cleaner down the TPS holes and throttle body. I then drove the truck about 50 miles last night and the idle seemed to be acting normal. Maybe my intake and throttle body need a better cleaning? Or unplugging the TPS reset something?

The random hesitation is still there though.

I will have to check for vacuum leaks and report back.