engine misfiring under load

[OwenArkwell]

Im new to this Whole forum thing so I apologize in advance if this is in the wrong spot but I have an issue, I have a 1997 2 door Tahoe with the 5.7 vortec and I can not figure out how to stop it from misfiring under load, have done plugs, wires, whole new distributor, updated fuel injection conversion, cats and so on. Ill be on the highway cruising at like 70 ill go to pass someone or go up a grade and the truck will start misfiring like crazy, and if I back off itll go away, but itll happen over and over again. Turning the A/C off helps make the misfiring not as violent but does not solve the issue, ive checked compression on all cylinders and there all 125-175 PSI. I have exhausted all my knowledge trying to figure out what is wrong with this truck. It is also worth mentioning that the truck is stock besides 32” ish tall tires.

 

[PlayingWithTBI]

What's your fuel pressure? s/b ~60+ PSI

 

[OwenArkwell]

I am not sure, I replaced the whole spider injection module which I believe has the pressure regulator already on it, and I dont think I dont think I mentioned this but cruising the truck runs 14.7ish:1 and under load it runs 12:1, and you can smell that its running rich and Today I pulled the plugs for the third time and some I can smell fuel on them.

 

[mr_josh]

Did you replace the spider assembly to address this problem? Did this issue start suddenly or get worse over time?

 

[OwenArkwell]

Did you replace the spider assembly to address this problem? Did this issue start suddenly or get worse over time?

started suddenly, replaced spider assembly with the updated fuel injection conversion thinking one of the stupid poppet valves wasnt atomizing fuel properly, but that didnt solve my issue. under brute acceleration (0-100) the truck doesnt seem to want to misfire but like getting on a on ramp and going from 40-70 or just plain going up a grade the truck misfires like crazy

 

[Glizzabeth_K1500]

My 96 k1500 is doing that exact same thing. And I've done everything you've done beside the injection system. I've gotten it to be at better. But still at 55-60 under a light load it'll misfire. My next gremlin to search. Cam sensor wires for a bad spot or short.

 

[SUBURBAN5]

I had this issue recently. But mine would fall on its ass when you would accelerate.. got bad enough to where it couldn't get up to 30mph.... I hooked up a pressure guage and drove around.... fuel pressure was the issue... when from 55psi down to 30psi... would of never guessed that since my pump was a new ac delco pump installed recently....... but fuel issue for sure... took a gamble... bought a new delphi pump, changed it in about 10min and took the truck for multiple test drives. Turns out that was the issue... after 2 weeks I took apart the old pump and confirmed the sock was clogged with debris....