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Discussion Starter #1
1997 Straight shift with no mods. Just a work truck.

Truck loses power and starts bucking. If you keep pressing the pedal or press it more it starts bucking. If you ease off the pedal to the point it stops bucking your are slowing down. If you push the clutch in let the rpms settle out you can just let the clutch out and keep driving. Though I had this problem fixed drove over an hour from home and it started up again. Just kept driving it and pushing the clutch in and got home without it dying or anything else. Acts like its starving for fuel.

What we have done. We have a parts truck and another one other so we have swapped a ton of parts.

Dropped and cleaned fuel tanks, fuel tank selector, lines all the way to fuel filter.
Took fuel filter bowl and return regulator apart and cleaned also.
New ford fuel pump psi is 55 at idle. new lines to pump
Borrowed scanner have 500+ psi on hpop and seems good psi when you drive it around. Could not get it to stall while I had the scanner to check hpop pressure during stall.
New Cps ipr icp (All Ford Parts) - new pig tail to cps because it looked kinda beat up
Swapped out hpop with another no effect.
unplugged map sensor didn't help
Injectors and gp were replaced a month before it started acting up.
Swapped out computers which didn't help.

What did we miss? Could something be causing it to defuel? Is there something else in the fuel system I could have missed?
 

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Have you done a buzz test?

Did you replace the UVCH and valve cover gaskets when you did injectors and glow plugs?
 

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Discussion Starter #7
What fuel level is in your tanks when this occurs? Almost sounds like you are sucking air in the lines.
full and i had one of the pickup broken off in one tank and knew about it. It doesn't act like air. It runs too even if you just push the clutch in and let it return to idle. It doesn't spit and sputter or surge it just evens out and you can dump the clutch and go. It might do it 30 sec later or wait several minutes depending on how your driving. having one of the pickup broken off I know well what air feels like. Driving aggressive seems to make it worse.
 

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Seems like an odd issue with all the troubleshooting you have done. Almost seems related to the HPOP system or intermittent electrical hiccup.

Might need to trace the wires or hopefully have live data during the next occurence. Only time i've experienced this was a failing ICP but that came with stalling as well.
 

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Discussion Starter #9
Seems like an odd issue with all the troubleshooting you have done. Almost seems related to the HPOP system or intermittent electrical hiccup.

Might need to trace the wires or hopefully have live data during the next occurence. Only time i've experienced this was a failing ICP but that came with stalling as well.
I agree but I have done everything to the hpop I can think of. Im down to swapping out wiring harness and trying to figure out if i have missed a sensor that can cause it to defuel. I have another truck that runs and swapping wiring harnesses out with it to see if problem jumps trucks is next thing but we are just guessing and doing maybe this will fix it work now.
 

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Discussion Starter #10
I agree but I have done everything to the hpop I can think of. Im down to swapping out wiring harness and trying to figure out if i have missed a sensor that can cause it to defuel. I have another truck that runs and swapping wiring harnesses out with it to see if problem jumps trucks is next thing but we are just guessing and doing maybe this will fix it work now.
for got to mention we did suspect the wiring harness pulled it off truck and took all the covering off of it and went over it and looked for worn wires and didn't find anything. it would have to just be broken inside or at one of the connections has gone bad. We replaced the cps plug because it looked like someone bent and straighened it but it didn't fix anything.
 

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my truck had this issue multiple times due to different issues this year

1. injector o rings pooped the bed at 311k put on a tuner and went to get up to speed, and truck would buck, back to stock it was fine. played back and forth and kept occuring. sold tuner to a guy at work that night went to roll up to sonic. got 100 feet from the house and it began bucking on a stock tune no tuner or anything. got home and checked oil......there was NONE on the dipstick. o rings had went and pushed my oil into my front tank. o ringed my injectors and cleaned them up good as a guy could without teardown and all was well.

2. bucking occured after a bowl delete few days after i did the delete. looked for anything i could threw a few parts at it, put some fuel from the shrader into a cup and it looked like it was not quite green.(o rings were about 1k miles from going fully bad). tank would leak if fueled up to the top so i dropped the tank and pulled it all apart....the pickup on the top of the tank on the outside had a hairline fracture and assuming under heavy throttle would suck tons of air into the system and begin bucking. fixed this with a new tank and an inexpensive sump from ebay with a 3/8 feed going to my selector and utilizing the factory return connection and capping of suction side with hose and a clamped on hose plug. works great and no longer can run out of fuel if a strainer breaks off.

3. icp had oil in the connection and would raise a cane under hard accel and would buck kick and spit intermittently. ebay cheapie for the win to get er goin. knock on wood still goin good on it.

4. not related to this truck but our shop has a 6.0 f450 that sits for months before use. extremely dead batterys caused bucking like mad while trying to drive it. batterys were too low to run the truck but could be jump started.

5. check all of your ground connections. all it takes is one dirty connection point to send it down hill
 

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lpop issue or oil pickup tube would be my guess. Next time it acts up immediately shut off the engine and check the HPO level at the inspection port....should be no more than 1" below the top.
 

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Discussion Starter #13
lpop issue or oil pickup tube would be my guess. Next time it acts up immediately shut off the engine and check the HPO level at the inspection port....should be no more than 1" below the top.
Thanks I'll put that on my list of things to checkout.
 

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I finally got to check the high pressure oil while it was stalling and i have a leak somewhere. Pulled any suggestions on where to start besides injector orings because I have already pulled and replaced them with no change. Also swaped out hpop.
 

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recommend you let the truck get good and hot with the valve covers easily removed. look at your rail plugs under the valve cover for leaks, aswell as oil squirting from oil spouts and check for oil coming out around an injector or two. not supposed to do that. not uncommon for o rings to go bad especially if they werent motorcraft(knock on wood for me lol)
 

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I finally got to check the high pressure oil while it was stalling and i have a leak somewhere. Pulled any suggestions on where to start besides injector orings because I have already pulled and replaced them with no change. Also swaped out hpop.
As @greenskeeper pointed out, maybe it is a supply problem, assuming " and i have a leak somewhere" means the oil tank level was low
Have you checked the base oil pressure yet?
 

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whats the condition of the oil? ive heard old oil can cause plenty issues. what color is your fuel at the shrader valve. green or blackish? couldve pushed your oil into your fuel tank and your running low on oil. just thoughts
 

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I finally got to check the high pressure oil while it was stalling and i have a leak somewhere. Pulled any suggestions on where to start besides injector orings because I have already pulled and replaced them with no change. Also swaped out hpop.
explain. Was the HPO reservoir low on oil? How did you determine the leak?
 

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Discussion Starter #19
actually had snap on scan tool plugged in and could watch oil pressure drop as it started to stall out. Could this be caused by something electrical. It seems to random to be something like orings. I will run fine for hours and then act up every 5 minutes.
 

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Air in the oil -- low base oil pressure -- just a couple of items
 
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