The engines in these models have individual ignition coils for each cylinder. Each coil has a boot on the bottom that connects directly to the top of its
Spark Plug. Whenever spark plugs are replaced, the coils/boots are removed to access the plugs. Examine both the boots and the coils for any signs of carbon tracking, cracks or other damage. Clean them with a dampened cloth and dry them thoroughly before installation. Examine the spark plug boots and the individual ignition coils for signs of damage.