HELP PLEASE! I am helping a guy work on a 1997 1500 4x4 4l80e. It came in from a couple shops with some issues that I have addressed one at a time. It needed some battery cables, that semed to fix the intermittent stalling. It would cut out intermittently like the key was shut off and on in about a tenth of a second, but stay running. The shifter cable was broken at a previous shop and the bolt in the shift lever was gone, new cable and bolt now.
After checking it over I put in a new stanadyne pmd, the new grey one, a new harness from the pump and made a bracket for mounting it on the cooler behind the bumper and soldered and shrink wrapped up a harness from 7wire trailer harness. The lift pump is new and makes 7.5psi KOEO and 5psi KOER and will drop to about 2psi when you rev it up. Filters are new, everything looks ok on the scan tool, no codes, boost goes to about 14-15psi. It runs very strong from cold start until 30-45 minutes of run time then it acts like it pulls harder at 1/2-3/4 throttle and will not go past 70 under full throttle but will go past 80 if you lighten up on the throttle a bit.
My next thought is maybe I have an injector or two that aren't holding pressure in the system. He has ran 3 tanks of fuel through with good cleaner/treatment. It doesn't smoke hardly at all, no black, the cat is gone. Truck was purchased running crappy, at least the stalling and cutting out is gone, now I need to find the last little problem.
thanks for any ideas. I also have fuel leaking onto the oil pan, but I do not see anything leaking from the top down. He also claims it was down to 8mpg before.

The filter sock in the tank may be restricted. The fuel manager O rings have a habit of leaking as well as the rubber hoses attached to it. Try to look under the intake to see if it is wet.

I have the same exact problem with mine its that to a tee man and ive done everything i can think of and still havent figured it out but i havent done the filter sock yet so i guess thats next unless you try that first and tell me it didnt help anyway maybe one of us will solve this prob and help the other ive done two new lift pumps, pmd, and relocation to bumper hole, the o.p.s. relay mod, new fuel filter and houseing, k&n air filter, new fuel shut off solinoide, now im doing the turbo had a lot of play in the shaft almost hitting housing, new fuel pump relay, tons of grounds problems but i think i got those fixed but still have the same old PROBLEM!!!!!!!!!!!!!!!!!!!!!!!!!!!! as you do my phone number is 828-303-0502 call and maybe one of us or the awsomeness of this site will help us ive gotton everything from this site and belive me its the only reason my trucks not in the junk yard and i love it so damn much for some unknown reason well thanks to all on here

Its wierd that it runs strong cold, when it should be using the most fuel and falls off hot, that is what throws me, also it maintains line pressure so it isn't starving for fuel. I am leaning towards injectors, but I sure wish it were something I could nail down before going through all of that work. Thanks for the help, lets fix some of these old dawgs up!

yeah im not looking forward to taking down the tank at allll ive been fighting with this for 5 months too ive found that running it with the fuel cap cracked helps a little but dont fix it so maybe it is the sock but im as dumfounded as you

check fuel pressure

check fuel pressure

X2

I already checked line pressure, are you talking about the injection pressure? I meant to say it pulls harder at 3/4 throttle than full throttle after running for awhile, not 2/4.
thanks

I think he means monitor it while driving to see what's going on. A plugged sock will act just like your describing it will run better cold because the crud on the sock will fall off and the more you drive it the more crud it picks back up. A fuel pressure guage will tell us alot about what's going on.

Kinda sounds to me like its defueling. High intake air temp or high boost will cause this. When this happens you do not always get a check engine light. It will perform better at lower RPMs when fuel consumption is lower. Once the foot goes down, the trans shifts, and the RPMs come up but the computer is only giving it "X" amount of fuel, so pushing it harder will actually make it lose speed. Once it goes back into O/D or the next highest gear, it will resume maintaining or accelerating. I've had this happen several times. Turn it off and restart it a couple times and see if it clears up. If it does, ill bet its defueling probably from high intake air temp if there is no check engine light on. If it has a manual boost controller on it, the boost could be a little too high, but not high enough to set a code.

Pumping in more hot air than required the burn the injected fuel will only increase the intake air temps, which pisses off the computer which then cuts you off. :D

thank you im going to look into that as soon as i get it back from havin the turbo rebuilt what do you think about the sock in the tank check it out to or