2003 5.0 GXI sputtering and backfiring at 2000 rpm underload

[katt68]

omg iboat wizards....I need your help
if I had hair I would start pulling it out....

so....boat runs fine, idles, revs in neutral....
underload when cruising...I try to get up on plane or faster at 2000 rpm....she sputters, backfires, tries, hitches and bucks....
I have
1. changed fuel pump assembly with new to rule out pumps'
2. changed check valve(anti siphon valve)
3.changed IAC
4.Changed TPS
5. ran new fuel hose to tank
6. new cap,wires and plugs

only thing left as far as I am concerned is the injectors....which are sent off being tested and cleaned....

could they do this?

like I said....beyond frustrated....
need help!

 

[Scott Danforth]

first, stop throwing parts at the motor

start with the basics, what is your fuel pressure. is it 43psi or higher, yes or no? if no, chase the fuel system (including the fuel vent on the tank and the strainer inside the tank pickup tube) if yes, then plug in and check all parameters

being fuel injected, at a minimum, you MUST plug in and see what your ECM is seeing, otherwise you are just pissing money away by throwing parts at it.

 

[katt68]

pressures are good, 50psi and 10...
strainer and suction tube checked....
vent tube is a mystery on my boat....

 

[QBhoy]

Run it off a remote tank with known fresh fuel.