A backfire is a loud popping or banging noise that occurs when the air-fuel mixture in the engine combusts in the intake or exhaust system rather than in the combustion chamber. Backfires can happen in both gasoline and diesel engines, and they can occur during acceleration, deceleration, or idling. There are several potential causes of backfires in a car. Some of the most common include: -A lean air-fuel mixture: If there is not enough fuel in the air-fuel mixture, the fuel can ignite in the intake or exhaust system rather than in the combustion chamber. -A faulty ignition system: If the ignition system is not working properly, the spark plugs may not ignite the air-fuel mixture at the right time, causing the fuel to ignite in the intake or exhaust system. -A vacuum leak: A vacuum leak can cause the engine to suck in air, which can disrupt the air-fuel mixture and cause backfires. -A clogged air filter: A clogged air filter can restrict the airflow to the engine, which can disrupt the air-fuel mixture and cause backfires. -Worn valve seals or faulty valves: Worn valve seals or faulty valves can allow the fuel and air to leak from the combustion chamber, causing the fuel to ignite in the intake or exhaust system. -Exhaust leaks: If there is a leak in the exhaust system, the combusting gases can escape and ignite in the air, creating a backfire. It’s important to note that Backfires can be caused by various problems with a car’s engine or exhaust.