10/16/2026
Coil-on-Plug (COP) Systems on Most modern vehicles use an individual ignition coil for each spark plug. If one coil goes bad, the cylinder tied to that coil will misfire, causing a hard start, rough idle, or shaking, but the car will usually still start because the other cylinders are still firing. However, if multiple coils fail at the same time or a shorted coil drains system voltage, it can prevent the car from starting.