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.