In the old days of carberated engines, it coud happen through the carberator, with the timing being off just enough to allow by pass from the valves back through the carberator. Through the tail pipe, gas fumes build up in the exhaust system and are ignighted. Either way it indicated an undesireable out of tune engine.
A car can backfire and die if the spark plugs are bad. The car could also have a problem with the timing or the catalytic converter .
it doesn't or it shouldent'
Slowing down
catalytic converter?
No! A car backfires because unburned fuel is getting to the muffler. The heat of the exhause system causes the fuel to combust, thus a backfire. A bad alternator will just not charge your car battery.
Could be in need of a tune-up.
A sparkplug misfiring.
Its either too much fuel coming from the carbeuator and causing it to backfire or it could be spark plugs wired wrong. try to be more specific on where backfire is coming from. either out of the carbeuator or the tailpipes.
bad compression
Your car is running too rich.
Possibly because its old!
Backfiring is a timing issue.