ok so i have a 91 ef converted to mpfi with a b18a swap so its obd0, i was pulling a cel for fuel pump so we changed it out to a walbro pump cause the car is slowly getting built so no need to go back to stock, that dident fix it so we added new fuel filter, bdl fuel rail, new injectors, just about every aspect of the furl system is brand new, when i was running 310 rc injector the motor shook so bad you could hear the axles vibrate so we went back to stock injectors and it calmed it down a bit but now the problem is when your driving normal its fine but as soon as you give it half to full throttle it sputters bad and back fires and we canot figure out what the problem is. also the cap,rotor, plus, and wires are all brand new. any help is apreciated

 

Have u tried a different distributor?

 

Just an idea (after reading both of your threads-honestly you only needed one thread but whatever) but if you're dumping that much fuel into your combustion chamber without adjusting the air/fuel ratios aka fuel maps then yeah, that COULD be your problem. In short, if you're running a stock ECU and bolt ons I don't think all that extra fuel is doing you any good.

I could be wrong, but that's my initial guess without having the car in front of me to tinker with.

There are other things that may be related, TPS out of spec, wiring giving bad feed back to your ECU to/from the pump, distributor on it's last legs, etc.

 

alright thanks guys and the reason i broke it into 2 post was because i dident want to ask too much in 1 and get less answers