Spark plugs use electrical current from the distributor or ignition coil, carried through the spark plug wires, to create a high voltage arc and ignite the air / fuel mixture. Spark plugs come in many different types, including copper, platinum, iridium and a number of configurations that provide different benefits. When replacing plugs, many technicians recommend replacing the spark plug wire set as well, although this is not always required.
Spark plugs can become fouled up a number of ways, or sometimes may just need replacing after extended use. A fouled or worn out spark plug will not provide as powerful of an arc as one in good running condition with proper gap, and as such will not ignite the air / fuel mixture as efficiently and decrease performance.
When replacing spark plugs, care should always be taken not to damage the threads. Since the spark plugs also seal the cylinder, if the threads become damaged the vehicle could lose compression which will result in a host of problems. Never replace spark plugs while the engine is hot! Metal at an engine's operating temperature is much more susceptable to damage as it become malleable with heat. It is also important to ensure no debris falls into the cylinder when replacing plugs. Typically pressurized air can be used to blow away any loose dirt and debris before removing a plug.
We carry a wide variety of plugs from these manufacturers: