First I want to say thank you to all who read and post in this forum the knowledge is immense.

I literally just got this truck 1 week ago. '05 6.0 F250. I have read numerous other threads and have not found an answer. I will start from the beginning.

I was driving on the hwy and once the engine is hot and I am over 55mph the truck feels like it wants to stall. The rpms drop and come right back up. Its like a 'hiccup'. If it starts to act up and I pull over it remains at idle and not stall. Once i get back on the hwy IF I go over 55mph the truck will stall and I will not be able to start until cool.

After doing some reading through the forums I replaced the IPR on the HPOP.

I tested the high pressure oil system. I took off the valve covers and tested both the right and left side individually, with the IPR valve open and close; cannot find a leak.

I took the fitting off of the top of the HPOP and tested with air there as well. I only hear air out of the weep hole in the back behind the gear on the pump.

I took the oil pump off and charged the branch tube with air, no leaks.

I checked all the dummy plugs. They have been already replaced with the upgraded ones and the orings all looked good.

I took the upper half of the standpipes out - look good, orings looked good. I was unable to get the lower half of the standpipe out on the passenger side due to the air box and the driver side only the top half came out when unscrewed from the oil rail.

I put it all back together with 2 new batteries.

I started it, (started cold), drove it 25 miles and it stalled, let it cool down and it started. Drove it 20 more miles and I pulled into a parking lot and I shut it off, and it started right back up 3 times. When it shut it off on the highway I unplugged the ICP sensor and it did NOT start.

It runs fine until I go over 55mph then I am getting the same stall issue. I can drive it around under 50mph and have no issues. I drove it under 50mph and shut it off a total of 3 times and it started back up no problem. If I drive it over 55mph rpm gauge drops and then comes right back up and IF it stalls I cannot start until it cools. Once it stalls out, If I try to crank on it, my IPR is 84.8% IPC - 99-120.

I am using a Scanguage II at idle
ICP - 18.5
IPR - 585
FMP - 47.5
my FICM Voltage stays between 12.5 - 13.0 while running.

I am at a loss. I feel like it is an oil leak somewhere, but I cant find it. All help is welcome.


**Does have updated STC fitting. I did not take it out to check the orings because I do not have the alignment tool to put it back together.

 

Probably that o-ring you didn't check. Waiting to cool the oil before a re-start is a leak, it builds pressure easier with cold oil. The high IPR indicates a leak, but shop air pressure can't go that high (2000psi) and once the pump hits that pressure, it leaks.

New dummy plugs and standpipes with the Teflon rings?
Try an air test using nitrogen, that will hit 1800psi and should find your leak, do it when the motors warmed up.

 

I am wondering if you have a fuel issue. You need to watch your fuel pressure. It should not drop below 40 pounds.

 

Hmmm.... I don't know about the rest of your guys but the alt volts at idle looks low to me. Should be 13.6-14.2, I'd check the Alt output and go from there.

 

Shouldn't be lower than 45psi.
The OP said he has to wait until cool. If it was fuel, a key cycle should resolve it. Still worth checking, especially if the blue spring isn't done or its possible not effective. Rental gauge from a parts store is easy to get.

Plugs and pipes torqued to 60lbs?

 

Yes teflon rings. How do I test it with nitrogen?

 

I wonder if you've got fuel and HPO issues. Fuel driving the stalling, and HPO driving the restart.

I would check fuel pressure as recommended and change both filters, if not already done.

Sounds like you'll need a stouter shop test for the HPO.

Can you get Scangauge data during the event?

 

Scanguage results during the event. All are normal except for the ICP it shoots up to 85. I do NOT have the fuel pressure gauge. I will look into getting one.

 

You could remove the FICM relay, use the remote starter wire on the passenger side and with valve covers removed, spin the motor watching for an oil leak.
Observe injector top seals/nipple cups and any oil leaking from the standpipe area. That should get you over 500psi.

 

Rent a nitrogen tank from a welding supply Shop, buy the fittings or borrow them.

 

The IPR shooting up to 85% is because it's trying to compensate for a leak that is opening up at higher oil temp.
Are you SURE you have the update STC fitting? If you do have the updated fitting, Did you check to see if the retaining lock nut was tight? That nut is what seals the oring.
Here's what the two look like.
Left: old STC design that commonly leak.
Right: new design with locking nut, sealing washer, & oring.

 

Higher temps and/or higher pressures, most likely both.

 

Right. Speed is irrelevant I think in this case. Speed is just adding load which in turn is heat in the oil. That heat in the oil is what is bringing on the leak then a no start.
I've shared this before where I had one that was so temp dependant it was to a single degree. That was the STC fitting above. I got a video somewhere.

 

To add, monitor and record the oil temp when the failure comes on. Then for testing, get it to that recorded temp and immediately do an air test and see if you pick up on the leak.

 

That and I think it's also pressure related. Hot oil leaks easy, that opens the crack and then the higher pressure is directing more towards it, trucks falling on its face. Oil cools, crack closes, oils thicker, truck fires and runs until it hits temp and pressure drops... hard to nail down due to
1) temps needed to induce
2) can't reach the pressure on shop air
3) trucks cold when tested, leaks not showing.

Could be hard to find, but Pete and I have given good recommendations to find this leak.