I have a back fire situation at about 2100rpm, before this and after this the motor runs great. Even when its backfiring the BLM is around 128. I checked for miss fireing plugs and wires. At first I thought maybe a VE cell was way out that wasn't it. I even tried leaning all the cells out at around 2000 rpm, but it still did it after. My accel inrichment didn't change anything either. My rotor and distributer are new. I'm thinking maybe the one injector on the passanger side of the motor, which doesn't get read by the O2 sensor is causing the problem. Does any body have any Ideas? I have a 747 ecm.

 

Give it more timing if it's backfiring through the intake manifold. This was a problem that took me a LONG time to figure out. Add 4 degrees to the cells around it and call me in the morning .

 

Thanks J, Makes sense because my new heads and intake have a totally different flow characteristic than the old stuff. I'll see if timing helps.

 

I added adout 3 deg from 2000 - 3000rpm, problem solved!

U the man J, Thanks for the help.

 

WoW....that's quick....Home of the Guru's

Stan

 

I just went thru the same crap on my friends T/A.

More AE (accel pump) will help also. His was too lean and given the engine combo needed a massive AE vs. MAP.

 

Thats weird, I had to decrease my AE by 1/3, to stop it from popping. My new motor, which probably has 90 more ponies than the old 300 horse motor, is less volumetricly effiecnt below 3200, so even the stock AE was just to much. But 3500 - 6500 she sucks back the gas now.