How To Use An Engine Vacuum Gauge?
Vacuum Leak Test Troubleshooting Engine vacuum Leak Issues Helpful Information Most internal combustion engine's hold between 15 and 18 inches of vacuum when idling. This condition varies as the engine is loaded, the amount of vacuum is measured by a combination of sensors such as mass air flow (MAF) and throttle position (TPS) or directly using a manifold absolute pressure (MAP) sensor. Engine vacuum is a large factor in the equation of fuel management which is determined by the computer. To aid in the discovery of a vacuum leak an audible hiss or whistle sound might be heard which will help pinpoint the problem. Engine vacuum is used to operate several accessories such as the power brake, climate control, (heater, air conditioner) and cruise control systems. Engine pistons create vacuum on their downward stroke which allows the air/fuel mixture to be delivered into the combustion chamber. (Air only in direct injection engines.) Symptoms of an engine vacuum leak include:...