2011 Mazda MX-5 Miata - Ignition Coil Boot

What Are Spark Plug Boots?

The coil boot, also called an ignition boot or spark plug boot, connects the coil pack to the spark plug and helps insulate the voltage from the coil to prevent it from arcing to the engine. Newer vehicles have the coil boot attached to the coil and the spark plug, which is commonly called a coil-on-plug ignition system. The coil boot is made of rubber or silicone and can wear out, split, or suffer other damage over time, allowing power from the coil to arc to the cylinder head. This prevents the spark plug from receiving the power it needs to generate spark, which can cause an engine misfire. When replacing the spark plugs or ignition coils, it is also a good idea to replace the coil boots to ensure continued ignition system performance and maximum efficiency. A damaged ignition coil boot could also lead to a rough idle, an active Check Engine light, or stalling in extreme circumstances - however, these symptoms may also point to a failing coil pack or spark plug. O'Reilly Auto Parts has How-To Resources to help you diagnose ignition coil problems, and carries the right spark plugs, coil boots, and replacement ignition coils to complete your repair.