Back firing? Is it bad for a motor?
 

I have a 3.8 with ITBs and Electomotive tech3. After hard acceleration up through the gears and then down shift with no throttle (Foot on Brake) my motor back fires a few times. Is this bad for the motor?

Not bad for the motor, but not great for the exhaust system.

It's likely caused by no fuel shut-off on over-run, so you're dumping fuel into the the muffler. There's occasionally enough oxygen to cause a secondary combustion in the muffler or pipes, usually due to a short, unrestricted exhaust system.

Don't you have a throttle position switch that will cut off the fuel?

Yes, but I am not sure it is cutting all the fuel off. I am going to have the motor put on the dyno soon to dial things in more.


Thanks for the replies.