have a problem

[dieselcrazyw350]

i cannot figure out the problem my truck has.
at certain rpm's it feels like it is cutting out or has a bad miss and some rpm's it feels fine???
at around 1500 it feels like its cutting out but if i go a little bit over 1500 it feels fine but then once i get at 2000 it starts to cut out again but once i go over 2000 it runs great.i replaced my lift pump and my water/separator is brand new and i also bought a pressure gauge with the tapped banjo bolt and ideling my fuel pressure is about 5psi and whn i rev it up high it still stays where it should be so im not sure.
could bad injectors be causing this? my truck has a little bit over 300,000 on it.
my truck is a 91.5 with a getrag. my smoke screw is bottomed starwheel is bottomed and the full power screw used to be only one turn back from bottomed but once it started doing this i backed it out about 1 1/2 more turns thinking i wasnt getting enough fuel but it didnt help one bit
so i have no clue as to what the problem could be.

[ahale2772]

did you do a fuel filter at the same time?

[dpuckett]

Could be your injectors, esp with your miles. Get them checked.

What is your fuel pressure running down the road, or when it acts up? Low pressure will cause issues, too.

Dan

[dieselcrazyw350]

yes i changed my fuel filter when i replace the lift pump but it didnt help.
i only have the fuel pressure gauge in the engine compartment right now so i dont know what it reads while im driving but im thinkng about running a long line into my cab temporarily to see what she reads.
the injectors from what i can tell are stock but not sure

[dieselcrazyw350]

*update*

ok i rigged my fuel pressure gauge into my cab temporarily and it stays 5-6 psi and when i floor it it only goes down to 4 psi.

also i decided to see what happened when i free revved it to the rpm where its the worst which is 2000 and i could here popping from the exhaust(i have a stack and had my back window open) while fuel pressure read 5 psi