My motor is completly rebuilt. Its got like 100 miles on it. Its got a cam and all the good just that go with it. When I let off and the rpm's are droping it backfires at about 2100 rpm. I have the pcm programed so everything should be working fine.

 

anyone have any idea at all???

 

I am having the same problem. I am thinking either it is due to incorrectly gapped plugs, or unburnt fuel in the headers. I am going to let my car warm up to normal temp first today and then drive it around and see what happens.

I was searching and people were saying its normal for it to do this when the car is cold because the unburnt fuel hits the exhaust and it explodes, making that popping noise.

 

mine's doing this every once in a while as well. i was told it's either the plugs or an exhaust leak. I'll be changing the plugs soon anyways, but let us know if you figure it out.