The number of low-quality replacement coils in the marketplace is rising and this can have detrimental effects on your car if you use them.
Low-grade coils can induce misfires and trouble starting. Coils depend on fly-back voltages that are fed back after the spark plug has been "fired" since they are regulated by the engine management computer (ECU).
Unfortunately, these voltages created by the cheap ignition coils may be extremely high, causing the ECU's ignition drivers to fail. In turn, this will causing damage to the ECU which may lead to costly repairs.