Spark plugs are responsible for providing an ignition source inside your engine's combustion chamber. Energy is transferred from the ignition coil to the plug which creates a spark igniting the air fuel mixture. As an engine begins to age a spark plug can become fouled which can lead to poor performance, poor fuel economy, and hesitation. On modified vehicles this occurs at an accelerated rate compared to a factory car. Replace your fouled spark plugs with a new set of spark plugs.