When it comes time to do a tune up on your 79-93 Fox Body Mustang, spark plugs should always be on the list. Spark plugs are fired by your spark plug wires to ignite your air and fuel inside of your combustion chamber. A fouled or damaged plug could cause your plugs to misfire giving you a rough running engine, sometimes referred to as a "miss". Having a misfiring engine causes poor performance, decreased fuel economy, and sometimes a no start condition. Replace yours today and get your Fox Body running right again at Late Model Restoration.