What makes a car backfire?
Answers:
When you switch off the car, you can get fuel still being pulled into the cylinders, but not fired, since the electricity to the engine is switched off. The raw fuel can then find it's way into your exhaust system, which can be ignited when you restart the car. This can happen on cars with carburetors. This type of backfire does not hurt the engine, but can destroy your exhaust system. Try to let your car idle a minute before you shut it off to minimize the fuel charge into the cylinders.
Modern cars don't do this because most are now fuel injected and the injection of fuel is stopped when you turn off your key.
A buildup of raw fuel that accumulates in the exhaust for various reasons. Once that fuel builds up it can ignite causing the backfire
Have your timing adjusted
ENGINE TIMING IS OUT/
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