'88 C2500 won't accelerate

[catback23]

My buddy has an '88 C2500 pick-up truck with the 350 5.7L TBI. The truck runs pretty good at idle and in park but once you put it in drive it starts to act up. It's as if it's cutting out when you try to go, sometimes it even cuts off. He's tried changing the distributor, coil, ignition module, fuel filter, and fuel pump to no avail. He thinks it's a fuel problem with a lack of fuel causing the problem but he's stumped because it only cuts out when the engine is under a load (in gear). Has anyone experienced this and/or know how to go about remeding it?

[2000CAYukon]

How does the spray from the injectors look when the air cleaner off? A fuel pressure test should be done.

A blocked exhaust can also cause no acceleration. Might try to remove the cat just to see if the problem goes away.

//2000CAYukon

[Wheeler88]

After everything else, check each plug wire for proper firing order and that your wires are not arcing to metal or each other.

[jveik]

yeah maybe the cats clogged. its the same as if you were to plug the end of the exhaust pipe with the sole of your shoe... (i killed my dads honda accord by pushing my foot over the end of the pipe until there was so much back pressure that it died) this may be his problem and its more likely to be the problem if he burns oil and since its an 88, id assume it burns at least a little bit unless hes really good to it lol

[catback23]

Update: The fuel injector spray looks good and strong although I haven't watched them when the truck cuts off. The truck idles pretty good and revs up to a certain point pretty well so I don't believe the cat is clogged although it is still a possibility. What the truck is doing currently since we changed the distributor (again, the distributor was fucked up) is idling well and reving up until it reachs the cut off point where it'll just die if you hold it there or beyond, if you let up it'll keep running. The whole throttle body was changed just yesterday and that didn't do anything. I'm thinking there is a fuel delivery (flow per min) or maybe an ignition/valve timing issue (I favor this one less than the fuel). Any ideas? I'm thinking it doesn't matter if it's under a load because it dies anytime the throttle goes too far. What are the odds that it's a computer/electrical/sensor issue considering that it runs and revs a little and that just about every component in the computer system has been changed including the computer. Any thoughts or things I can eliminate as being the problem?

[airdale94]

Originally Posted by catback23

...The whole throttle body was changed just yesterday and that didn't do anything....I'm thinking it doesn't matter if it's under a load because it dies anytime the throttle goes too far. What are the odds that it's a computer/electrical/sensor issue considering that it runs and revs a little and that just about every component in the computer system has been changed including the computer. Any thoughts or things I can eliminate as being the problem?

Maybe the TPS (throttle position sensor). Did you reinstall the old one when you swapped throttle bodies? There is a voltage check that you can do on them, and I think some of them are adjustable.

[catback23]

Problem solved, this truck was running an external fuel pump (the very one that was replaced) and the in-tank pump and/or sock is plugged up and not allowing enough flow. Now just gotta drop the tank and replace the pump and sock like it should have been done when the pump went out.

Airdale94: we replaced the the whole throttle body with everything on it with another.

Thanks for the help everyone

[Wheeler88]

Interesting. I was wondering if I replaced my pump with an external fuel pump if I would have to drop the tank and remove the old pump and replace it with a short piece of fuel line.