fighting gremlins

[rabbit]

94 k2500 5.7 tbi 4l60e just did head gaskets swapped to edlebrock performer intake ultimate tbi mod injector spacer and throttle body spacer. truck wont run at 0~timing runs best between 4 and 6. unknown Miles on engine but odometer says 280. so my issue is that there is a intermitent miss and hunting idle, missing power through the powerband and kinda stumbles in the higher rpms at wot aside from that it starts first crank and runs great ish
replaced 02 sensor, plugs, tps, and rebuilt tbi unit. has the 96+ fuel pump @30 psi. with upgraded spring no afpr.
I've been fighting this thing since it went back together and I do not know where the timing was set before headgaskets
any thoughts? cap rotor and wires was done about a year ago but thats probably my next move.

 

[Schurkey]

Why do you need 30 psi of fuel pressure?

Connect a scan tool, verify EVERY sensor and computer output including spark advance. Look at the short- and long-term fuel trims.

 

[rabbit]

i needed to replace fuel pump and have read that its pretty common to use the vortec pump i dont need 30 psi its just what the pump provides, id imagine i want about half that around 14. I'll look into a scan tool

 

[Schurkey]

What is your ACTUAL fuel pressure?

 

[rabbit]

how would I go about checking that? tapping into the return feed?
it is at 30 going into the tbi the spring should is off Amazon claiming 28 29psi

 

[Schurkey]

The Vortec pump is intended to supply in excess of 60 psi, because the Vortec engine runs on 60-ish psi under load.

If you're seeing 30 psi with a 29-psi spring, you've got 30 psi.

WHY? What changed that you need that much fuel pressure? The only OEM application that used higher pressure like that was the later TBI big-blocks. Is the excess fuel pressure compensating for too-small fuel injectors?

Connect a scan tool, look at O2 sensor readings, cross-counts, and short- and long-term fuel trims. I suspect the engine is gargling on gasoline, which probably means the catalyst is poisoned, maybe plugging, too.

 

[rabbit]

what scan tool do I need, i also have a 12 - 14 lb spring I can swap in place of the bigger spring I didn't fully understand how that internal regulator working but I'm beginning to see . I've been trying to fix whatever issues with timing and fuel I was just starting to wonder how plugged the cat would be at this point. seemed like regardless of how it was running it was either too rich or too lean
I can get it to run pretty well either cold or hot but not both, I can adjust timing and runs great untill temps rise and then make adjustments warm to run decent and then wont start in the am

 

[rabbit]

orange tip fuel injectors btw same ones from before the head gaskets

 

[GMC LIGHTING]

Oi, you should only need the lower regulator spring pressure at around 14psi. I have the same pump as you (96 vortec), as I'm gonna put in a healthier sbc 350 with the equivalent of the summit 1103 camshaft. With that said, I also know that I'll need a new eprom (which I have and install when the motor goes in). And I also did the ultimate tbi mods by raising the injector pod. What's done to the engine itself? Or did I skim too fast through the thread...?

 

[rabbit]

as far as I know engine is stock, but thing is, with everything set to factory spec, engine runs but only barely, 0 driveability. 30lb s0ring and about 6* timing thing runs great, albeit intermittently throwing a code 44 leand exhaust...go figure...