Coil-on-plug Ignition

It removes the need for high-tension leads. It is the most common layout on modern petrol engines. Each coil can be controlled individually by the control unit. Use dielectric grease in boots if the maker recommends it.

The control unit switches each coil at the right moment for its cylinder.

Cracked rubber boots can let the spark leak and cause misfires, especially in damp weather. Swapping coils between cylinders is a quick way to confirm a faulty coil.