VACUUM SYSTEM: The vacuum system is created by the downward motion of the engine's pistons. This suction, or vacuum power, is used to help operate the charcoal canister, the EGR valve, the automatic transmission and the power brake booster, as well as on some cars, the distributor, heating and ventilation systems. The vacuum advance mechanism found at the distributor on some vehicles uses vacuum power to get the distributor to recharge or advance the spark to the spark plugs. On some newer vehicles, the control unit advances or recharges the spark electronically. The vacuum power is delivered to the various parts or systems via hoses and vacuum diaphragms. Vacuum diaphragms regulate the vacuum power to the various systems or parts they serve. Any worn vacuum diaphragm or any leaking or disconnected vacuum hoses may cause the system or part they serve to malfunction as well as affect engine performance by causing it to idle rough, stall or hesitate.
