Help with rough startup, and randomly dies on a rare occasion from sputtering too much. 98 sierra 4x4 5.7l vortec

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kingremy619

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This one is a pretty wonky one but suits me and my luck being (atleast most likely) something with fuel.
The truck honestly drives great 90% of the time and being on the edge of hitting 500,000km.
But when I go to start it up every single time it will sit there trying to start and alot of the time needs you to pump the gas a few times to get it going and up to a proper idle. It doesnt react as it should however when i pump the gas, I can tell it takes a second to start giving it fuel which leads me to believe the fuel pump is toast, but youd think it would **** out on the road alot more then it does if that was the case. I do notice it runs into less issues when above 3/4 tank, but its still not free of issues by any means.
Ive found the battery does have a bit of a loose connection sometimes like when i make her go sideways and **** and do run into more issues but I think the battery just adds onto my issue I dont believe its the cause, but then again im no mechanic as why im here haha.
Also has a fuse box bypass but it seems in pretty well working order as all electronics work beautifully.
It also seems to start shittier in the cold over warm temperatures, but warm temps still give me the issue. Ive tried the screwdriver trick on the injectors and tbh I cant say for sure unless I multimeter them but they seem to be in fine working order.
The sputtering is very noticable, it will do it occasionally as im accelerating usually between 60 and 80, but other then that it drives fine most of the time. But ive had 2 senarios now where its sputtered and died. It also tends to idle faster then normal before the sputtering happens, pushes 20-25kmh in idle which as far as im aware isnt right at all. Once and a while aswell the first bit of gas wont do anything and will jump a bit when it gets fuel. Has anyone else had this issue and could shed some light onto what helped fix or diagnose what the issue is exactly?
Any help is majorly appreciated.
 

Schurkey

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What is the fuel pressure at prime?
What is the fuel pressure under load?

How old are all the usual "tune-up" parts and procedures? Distributor cap and rotor, plug wires, spark plugs, EGR check, PCV and Evap system verification. How old is the O2 sensor? They get lazy with time and mileage. Air and fuel filters?

Connect a scan tool, verify EVERY sensor (emphasis on engine coolant temp, TPS, and MAP, but all of them in general) and check the computer outputs--EGR command, spark advance, IAC, and so forth. Check the misfire counts for each cylinder, and look at the fuel trims especially when the engine isn't running right. Make sure there's an RPM signal when cranking the engine. Make sure the distributor offset/cam retard is within spec at 1100 rpm.

Vortec engines are infamous for distributor problems--worn gears, wiped mainshaft bushings, faulty caps and rotors. Also known for injection spider problems, which are generally fixed by upgrading the poppet injectors to electronic injector assemblies--and at the same time, replace the lower intake manifold gaskets which are yet another trouble area.
 
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