What causes a car to backfire?

Answer 1

usually late ignition timing could cause this or an excessive amount of fuel in the exhaust system.

answer

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

Consider getting yourself a service manual as it contains many troubleshooting for your car. Comes very handy sometimes.

Can also be caused by crossed spark plug wires meaning they are not connected in the proper order

Also

Listen to the Signs of the Car talking to you,

Is the Backfire coming from the Tailpipe area or the Engine Compartment area?

Signs of backfire can be caused Vacuum Leak, in and around the Intake Manifold Base Gasket areas, and the Carb. Base or Throttle Body Base, and in any of the many different

Vacuum hoses/lines depending on your make or model, "Use Caution with what you use to seek out the Vacuum leaks, as many aresol base products contain a petroleum base

which can cause severe flash fires,

( especially on and around HOT Engine Parts & Faulty or Loose Plug wires )

in Running Conditions.

Always RememberSAFETY FIRST,You want to drive it after you fix it,"NOT look a pictures of its chard remains,in a Hospital Burn Ward."

Be Safe Now / Cruise Longer

It could also be the contact set / points gap if this has recently been replaced/ adjusted.