I just started am having a problem with the roadrunners 383 backfiring through the carburetor almost all the time. The only way not to have it do that is to keep the engine above at least 2500 RPM.

So just trying to drive down the street I sound like a popcorn machine. The carburetor is a 650 Edelbrock Thunder series and probably only has a thousand miles on it or so. I am running a Petornix igniter and just installed new Accell plugs and new Accell ceramic tipped wires just in case it was arcing through the wires and misfiring.

The thing is it wont backfire unless under a low RPM load (like running the engine in say at 2000 RPMs or so in overdrive) . I checked with my timing light and the timing chain seems not to be slipping.

If I keep the RPM's up it wont backfire, like say manually shifting from 1st to 2nd, to 3rd to 4th and it wont backfire no matter what I do unless under a load so I am stumped as what to look for next?

Could this be a issue with the transmission not in sync with the Throttle Position Sensor maybe?

One note is it used to do this exact same thing when the engine was not up to full operating temperature, but once it hit 180 degrees that popping would go away. Now it acts like this even at full warm up.



Any thoughts on why this may be happening all of a sudden??
Stu