because of low battery voltage
catalytic converter, oxygen sensor, exhaust leak
Unburned fuel in the exhaust system causes the backfire from the exhaust pipe.
Engine is running lean.
I dirt track race and mine did it once it was because it was running to lean.
The exhaust pipe will turn red when the engine is running lean. You may have an EGR valve problem, vacuum leak or other problems that can cause the engine to run lean. A lean running engine can burn valves or pistons and causes other problems. Whatever the cause, it needs to be repaired before you put more miles on the engine, otherwise you'll ruin it, if you haven't already.
It's lean.
Bank 1 fuel too lean Probable causes: Vacuum leak at engine, bad intake gasket, exhaust leak before an o2 sensor, map sensor
No who, but what. All internal combustion engines emit exhaust fumes.
It's lean.
A very fat girlfriend
gas from the exhaust
Broke rings on pistons