Ok how do you know if it's fouled
Ok, what he means by FOULING is the condition of the plug electrode. here are some pictures and an explenation of some of the plug conditions you may find when you take the plug out of the engine.
#1The spark plug in this picture has quite a few miles on it, but led a relatively good life. There's no evidence of bad tuning, carbon deposits, or of a damaged insulator. Note also that by reading the ground strap, we can see the heat range of this plug is right about where it needs to be. To read the plug and know if you have the right heat range, look at the difference in color of the strap. If the color change is too close to the strap's end (above the center electrode), the heat range is too cold. This means the heat is being absorbed too quickly into the base ring and is not able to burn off carbon deposits effectively. If the color of the strap changes too close to where it is attached to the base ring (the last thread ring), that means the plug's heat range is too hot. This means heat is not being transferred from the strap to the base ring quickly enough. A proper heat range will be shown by the different coloration actually occurring at half the distance of the ground strap. When running the proper heat range, approximately one thread on the plug will also show some discoloration.
#2 worn or rounded center electrode indicates excessive wear, and can definitely cause misfire under acceleration, hard starting. It may also cause reduced fuel economy and damage to other secondary ignition components (e.g., plug wires, coil, and/or the distributor cap). When a plug has this type of appearance, all that means is it has exceeded its life span. Notice the ground strap and thread base; this plug's operation was within the proper application of heat range.
#3Although this is an extreme circumstance, "bridging" (or the accumulation of deposits on the firing end of the plug) is influenced by oil leakage, fuel quality, and the engine's operating duration. Light brown deposits encrusted on the ground and/or center electrodes indicate ash deposits. When the deposits are found on only one side of the spark plug's nose, it's considered to be a problem within the cylinder head. This could mean either valve stem seals leaking or worn valveguides. When the deposits are found on both sides of the spark plug, it's considered to be a problem with piston ring sealing. This condition can smother the spark, and in some cases, cause it to misfire.
Hope this helps out
Glenn
