Laura, a car backfires because there is unburned petrol in the exhaust system, which is then ignited by burning exhaust gas. It used to be unreliable ignition systems that did it, often poor maintenance. Nowadays, of course, everone's motor is perfectly tuned.


If you really want to try it out, drive down a very steep hill, turn off the ignition, and let the dead engine slow you down. Depending on the length of the hill, when you restart the engine, you can open up the silencer(muffler in the USA) like a sardine can.

Some idiot boy racers turn the ignition off-and-on whilst racing on the flat to give 'gunshot' noises. As Big Mick says, if you've heard both, you can tell them apart, but possibly not with shotguns.