A device that is found in the ignition system that is threaded into the cylinder head which contains two electrodes that extends from the cylinder to form a gap from the high voltage electricity arcs is called the spark plug. It works in igniting the compressed mixture of air and fuel which allows the vehicle to run. It is actually considered as the “window” of the engine which can be useful as a diagnostic tool. In some cases, the spark plug is actually considered as a thermometer that displays the conditions and symptoms of the vehicle’s engine. Basically, the two primary functions of the spark plugs are: to ignite the air and fuel mixture and to transfer the heat that is produced from the combustion chamber. This spark plug actually carries an electrical energy that allows the fuel to work efficiently. It requires a sufficient amount of voltage that will be supplied through the ignition system in order to create a perfect spark right across the gap. The performance of the spark plug actually relies on its low temperature to prevent occurrence of pre-ignition yet, high enough to prevent the fouling condition. Take note that spark plug does not actually create heat rather eliminates it. Spark plugs are actually considered as one of devices in the engine system that is often neglected. But if you’re a true car enthusiast, you know how absurd it is to have a faulty spark plug and so once its condition fails, you make sure to have it replaced right away and you know that the NGK spark plug PFR6Q NGK will provide you the perfect quality that you are expecting from a spark plug device. For your 2003 Volkswagen Jetta, used only the F1000-87183 NGK spark plug PFR6Q NGK.