Q: What does it mean to gap a spark plug?
A: When you gap a spark plug you set the distance between the electrodes. The side electrode, also called the ground electrode, is the piece that protrudes out and makes an “L” shape. The center electrode is the piece that is in the center of the plug. The distance between the two electrodes has to be exact for the spark to fire correctly; otherwise the engine will not run efficiently. To gap a spark plug insert a wire gap gauge or a flat feeler gauge between the electrodes and adjust to the correct gap distance. The gap distance is usually given in thousandths of an inch. The correct gap distance should be on the EPA sticker in the engine compartment.