If your car's ignition system is failing, you may be wondering if you can replace just one ignition coil. The answer is yes, you can replace just one ignition coil. However, it is important to note that if only one coil is failing, it is likely that the other coils will fail soon as well. Ignition coils are responsible for providing the spark that ignites the air/fuel mixture in the engine's cylinders. Over time, they can wear out and stop working properly. When this happens, your car may run rough or stall completely. If you notice any of these symptoms, it's a good idea to have your car inspected by a mechanic. They will be able to tell you for sure whether or not your ignition coils need to be replaced.