Recently had to replace the AAP diaphragm because the idle was horribly rough. The last few weeks with the bad diaphragm I noticed once I got on the interstate and was going about 45 or so, it would sputter and hesitate like there was no fuel whenever I would go up any sort of incline and there was a load on the engine. I replaced the diaphragm and tried it again. But the sputteringa and jerking still continues. I didn't know if it sounded like the float in the carb is too low or what. But it doesn't do it until higher speeds >45 and when you would punch the accelerator or come into any kind of incline. Any help on diagnosing this would be great.

I'm assuming that by "AAP" you mean the "auxillary acceleration Pump"?
Did you also check the acceleration pump for proper operation? Your symptoms sound like the acceleration pump isn't delivering enough extra fuel when you push the pedal down....

Dave

so how would I go about checking this? is this a part to replace? or is there a way to take it apart and check it? my Haynes manual doesn't help me any with this part. Thanks.

Could be as simple as a fuel filter thats not letting enough gas through, I'd start there.

To test the acceleration pump, open the throttle while looking down the carb throat. You should see a healthy stream of gas.

Also check the float chamber window to see if the fuel level is where it should be.

Dave

If you haven't done a tuneup in a while, then do one. (plugs, wires, air filter, fuel filter, timing, adjust valves, PCV valve, etc.)
If it still doesn't idle, then look for a vacuum leak (disconnected or cracked vacuum hose).

the idle is fine. I am trying to figure out why there is hesitation and sputtering while accelerating on the highway, especially even the slightest incline. But thanks for the reply

Trickster...I am trying to find the fuel filter on this truck. Any tips?

Dont know about your truck, but mine (85 22r) is just ahead of the passenger rear tire, tucked up by the front of the bed on the frame.

To check the AAP, simply pull the vac line off it and see if there is gas in the line. If so, the diaphram is punctured and needs to be replaced. The AAP really only affects you when the engine is cold and you first step on the gas. It squirts a little extra fuel in for ya. Probably not your problem as I'm assuming this happens when the engine is warm as well?

The fuel filter is clipped to the inside of the frame right near the gas tank. Just follow the lines off the tank and one will lead you there quickly. Its a 2min replacement - very easy.

Now for your sputtering problem.. does this happen when warm or cold or both? I'm gonna guess warm and not cold - if so I bet your choke is not opening. This would cause the carb to dump too rich a mixture in the engine and cause it to flood/sputter. Which would explain why it only happens under acceleration - you're probably flooring the pedal dumping too much gas without any air.

To tell if your choke is opening - let the engine warm up to temp, pull the air cleaner cover off, and look at the top fo the carb. Ignore the drivers side choke plate - it is vacum operated and does its own thing. What you want to look at is the passenger side choke plate - it should be compeltely vertical. If it is not, then this is your problem.

Annnd thats the first thing I would check (again let us know what temperature this happens at as I'm currently guessing). I can probably come up with some more stuff to look at too..

-Scerb