sputtering

[mmcdaniels610]

have a 97 blazer i took it out to the mud but didnt go threw all that much a lil bit of water not alot, it is sputtering and running shitty when im going slow and slowly pushing the gas it will accelerate fine but if i push down on the gas hard rpms will drop and it will not accel

replaced the wires and plugs
put sea foam and injector cleaner in it
and replaced the fuel filter

if im in neutral and i put the gas to the floor it will make a popin noise and rpms will drop

took it to the auto parts store dianostic test said it passed

any idea what this could be

[old_master]

Have you checked fuel pressure and leakdown? Key on, engine off, fuel pump running, must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off.

[mcmalloy]

take the air filter out and try it , if its popin in nutral when your rev it could be a bad knock sensor , get it scanned to see what comes up

[mmcdaniels610]

nothing shows up on scanner fuel pressure gose to 52 and moves alot when running

[old_master]

GM does not publish ANY engine running fuel pressure specs. What is fuel pressure with the key on, engine off, and fuel pump running? And, does it remain above 55psi for 3 to 5 minutes after the pump shuts off?