Chevy Luv 4.8L Running Issues

[jordanpierce21]

Well Im excited to be a part of the board! But im having some issues with my swap.

4.8l w/ 4l60e
walbro 255( have also tried carter p5000)
No codes

The truck fires off at first bump every time and runs great and has all the power for about 30 secs. It then begins to really bog out and can barely pull its own weight and will backfire and pop. Could this be clogged injectors or a sensor? I tried another set of injectors and it ran better for a little while and then is back to how it was. I know the plugs are fouled and have new ones to go in but don't want to just wash out the next set as well. The weird part is that once it loads up i can put in Neutral shut off and restart and put in drive and it runs great again until symptoms reoccur, i can do this process all day. Im really stumped on this and am completely out of ideas.

[pajeff02]

Welcome to the site!

Is the engine wired such that you have an OBDII port to scan for codes? Are you running a stock GM PCM or an aftermarket controller? It certainly isn't warming up enough in 30 seconds to go into closed loop fueling, so it is not accepting feedback from the O2 senders yet. How about some more details?

[jordanpierce21]

Oem 4.8l ecu vats and emissions takin out by lt1swap.com. i have obd2 port no codes. When i unplug maf it runs worse.

[SMWS6TA]

Need to check pressure at the fuel rails. is this a new pump or a used one?

[jordanpierce21]

Both pumps were new

[pajeff02]

Still a good idea to verify fuel pressure. Does your fuel system have a return or does it deadhead at the rail?

[jordanpierce21]

K ill check pressure, its return style and i can hear it flow to the tank so its not jammed up.

[pajeff02]

How are you regulating your fuel pressure?

[jordanpierce21]

01 truck setup regulator on the rail