i have a 5.0 302 cid 1987 4wd f150 ...
when i step on the gas little bit the truck will sssssllllooooowwwwlllyyyy acclerate........put your foot on the gas any more and it just sputter out BUT WONT CUT OFF!i have replaced the egr, tps,checked for vacuum leaks...replaced both fuel pumps and i had the fuel pressure checked and in was fine...i took off the 2nd cat thinking maybe it was seized up and its still runs bad,the o2 sencer and the oil and fuel filters,....the truck will run fine when coldwhen i heats up it will do it ....no real trouble idleing...its ssoo strange ive been workin on this for months! any suggstions? plz help ima new guy 2 this form

 

you had the pressure checked? the sympyoms you are having sound like a fuel pressure regulator acting up.

go to your auto parts store and buy a pressure gauge, they are like 30 bucks,

 

How old is the muffler?

 

Could be the IAC also since it only does it when it is warm. Won't hurt to check it anyways.

 

the exhaust is only 6 months old and works like a charm IAC plz dont jump at me but what is it and what does it do ....also when i had the fuel pressure checked, it was checked where the fuel entered before the fuel rail........fuel regulator was replaced same thing

 

I have an 87 f150 2wd and have a similar problem, if I give too much gas especially in 3rd-5th the engine seems to do the same thing, much less severe if engine is cold. I have a new tank, pump, sending unit, fuel filter and have used many cans of seafoam incase it was dirty injectors and no difference.
Hopefully my post narrows some thing's down maybe and I subscribed to this thread and will post anything I find that's relevant.

 

IAC = Idle Air Control valve.

IDLE AIR CONTROL VALVE (IAC) Definition: An electrically-operated valve which allows air to bypass the throttle plate in a fuel injected engine to regulate engine idle speed.

 

Fuel filter??

 

no its not the iac because that was replaced also and if it was i would be cutting off in while idle(which it does) but it only happends when hott it can run for 2 hours and wont had a problem.(lol ive messed with this thing alot)i think its something to do with the fuel....and the fuel filter was replaced with a new one a month ago. if it helps any if u step on the gas it will accerate but slowly...u cant put ur foot all way down...it simply will just make a chokeing noise but doesnt cutt off ....does it while driveing which sucks.....going to try to put a video up idk if i can.....

 

My suggestion is engine electrical. Electrical components are at their greatest stress and tend to show problems when warm/ hot. They sometimes tend not to show a problem until engine is hot. I would check ignition coil, plugs, wires, pickup coil, and ignition module. I know that seems like a lot, but just go through the electrical system. When was last tune-up? Pickup coils can cause strange stuff and I bet yours was never changed. I would still have been inclined to say fuel/air problem, but you said it all checked out. it couldn't hurt to check with a can of carb cleaner for air leaks. Also, check timing.