An ignition coil is a high voltage transformer in your ignition system which transforms the battery's low voltage to the thousands of volts needed by the spark plugs to start your engine and keep it running smoothly. If your ignition coil is not working properly, it will not be able to create the spark to ignite the air & fuel mixture, causing a backfire or misfire. A bad ignition coil can severely damage the catalytic converter or engine. If you're experiencing a misfire, backfire, or other issues, have Brach's Auto Center in Chicago, IL, perform a diagnostic service. You can call Brach's Auto Center at 773-238-0606, or schedule an appointment online.