If your auto backfires while starting (not while driving) usually one of a few things is the culprit. 1. Is it wet? Most commonly, this occurs in "damp" conditions and can be attributed to moisture in the distributor cap. The humidity in the air causes some condensation within the cap and interferes with the ability of the distributor to function properly. 2. Carbs and Fuel Injection. If your problem seems more general in nature and occurs other than in wet conditions, you likely have a problem with your fuel injection system or carbuerator. Depending on how your car is equipped (fuel injected or carbuerated) you will likely find your problem here.