The ignition coil converts the vehicle’s 12 volts to the more than 10,000 volts required to produce an effective spark in the spark plugs, which in turn ignite the air-fuel mixture in an engine’s cylinders. Some cars use one coil, but increasingly, each cylinder bank, pair or even individual cylinder get its own coil. A failing coil can result in anything from rough operation or diminished acceleration to a complete engine stall (or a failure to start).
