what causes backfire
Answer   A backfire is caused by unburned fuel and air getting into a hot exhaust system where it ignites. Plugs have nothing to do with it. Some cars, when they ar â¦ e turned off, pass enough fuel and air, that isn't being burned in the now-turned-off cylinders to cause a backfire.
usually late ignition timing could cause this or an excessive amount of fuel in the exhaust system. backfire can be caused by choke not shutting off completely, also could have a bad distributor cap, bad spark plugs, bad ignition condensor, bad plug leads, or to much fuel getting to carburetor system.
A backfire is when the ignition of fuel doesn't take place in the ignition/combustion chamber, it(a backfire) can take place in the intake or exhaust. It can be ca â¦ used by a fuel to air ratio not being correct, also if the timing of the spark is not just right that could cause it to back fire.