Spark plugs play critical role in the engine combustion process by precisely igniting the mixture of air and fuel in order to produce power. There are several different ways of checking and adjusting spark plug gap with various pros and cons of each method. Most commonly you will see coin style and wire loop gauges being used, but feeler gauges are also used too. Here’s a guide to checking and adjusting spark plugs using the coin style and wire loop gauges, which will work perfectly in majority of cases.