94 gmc jimmy stumbles underload (cpi 4.3)

[ozzman5583]

it stumbles under load and i have no check engine lights on and idles fine and back fires through intake if i keep my foot pressed i have replace the entire fuel system except the fuel lines and even gas tank and i have replaced cap rotor the plugs wires and control module and idle air control valve and tps sensor map sensor and alternator and battery and ignition coil and blower motor and had the injector re wired to factory state and installed a cold air intake and radiator and temp sensor and knock sensor it has a lifter rattling fuel pump relay has been changed as well and a new converter

 

[kbold]

that sounds like the timing could be out by 180degrees.. or possibly even not holding compression in 1 or multiple cylinders..

 

[JRS]

I would check fuel pressure and verify timing then go from there .... either electrical or fuel pressure would be my guess ... good luck