7 Symptoms of a Bad Ignition Coil and Replacement Cost

An ignition coil is a part of the vehicle’s ignition system. It converts 12V battery power into high voltage in order to create a spark at a spark plug. The spark ignites the air/fuel mixture in the engine cylinders.

Most of the modern cars have one ignition coil per cylinder. Often, an ignition coil is installed right over the spark plug, like in this Ford engine in the photo. This setup is called coil-on-plug.

Spark plug wires transfer the spark from the distributor or ignition coil to the plugs that ignite the air-fuel mixture in the combustion chamber of your engine. This process starts with the ignition coil, which transforms low-voltage power into extremely high voltage. The transfer of this energy through the ignition wires creates heat, and over time, the wiring can become brittle, crack or breakdown. A weak or non-existent spark means the fuel in your engine’s cylinder will not be ignited. Depending upon how many spark plugs have failed, your car or truck will either run poorly or not at all. That’s why it is a good idea to ask the service department to inspect your ignition system whenever you receive a service.