A Toyota spark plug is constructed of both metal and ceramic components. The metal is at both ends and the ceramic is the insulator in the middle that keeps them separated. On each of the Toyota models that have been produced there is a separate spark plug for each cylinder of the engine. This ignition component is used in both types of ignition system whether it had a distributor or it is electric ignition. Because of the electrical arc that each spark plug generates produces a residue, the plug will become fouled in time, and its effectiveness in producing a strong electrical arc will diminish. Many Toyota owners actually pull their plugs at the half way point between tune-ups to clean and re-gap each plug. This increases the efficiency of how the plug operates. This can only be done once since the jumping of the electrical current does destroy the metal component just slightly with each time it fires. The only real precaution a Toyota owner should take when changing or cleaning their spark plugs is to be careful not to damage them. The only sure way to damage a plug is to drop it. This can in most instances crack the ceramic portion of the plug rendering it useless. It is the ceramic component of the Toyota spark plug that contains the concentrated electrical charge that is then generated for use by the electrode so an arc can be created to the ground on the exterior of the spark plug. A crack that may form is generally so small the human eye cannot see it, but when it is present the plug will not be able to transfer the electrical impulse from one end to the other.