If a car has an ignition coil plug problem, there can be a wide range of potential issues that could affect how your car runs. In particular, it may cause the vehicle to misfire, which can be a dangerous event when driving. Misfiring causes the vehicle to suddenly jerk or stall, and can lead to decreased fuel efficiency, increased emissions, and increased engine wear. In the worst cases, it can even cause catastrophic engine failure. Therefore, it is important to have a professional technician diagnose and fix the issue as soon as possible.