Failing ignition coils can cause sputtering, rough idle, hesitation on acceleration, misfires, and a check engine light. If not corrected, it can lead to catalytic converter failure and other problems. If one of your ignition coils is bad, it is a good idea to replace them all at once, to prevent future problems. The easiest time to replace your spark plugs is when your ignition coils are out. This kit contains Bosch Super Plus spark plugs and Beru ignition coils to service your entire ignition system at one time.