Engine Vacuum Leak Test

Steady low between 10 15 hg vacuum.

Engine vacuum leak test.

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. The engine control module ecm continuously monitors the environment in the engine. This reading indicates late valve timing.

This indicates that the engine s intake manifold or the intake gasket is leaking. Also a vacuum test can tell you a lot about an engine s condition. You may be able to hear it from inside the car but it is more likely that you will be able to hear it when you open the hood of the car while the engine is running. Check engine light low idle high idle poor acceleration cylinder misfire and stalling at idle.

Using the manifold absolute pressure map sensor or mass air flow maf sensor among others the ecm modulates fuel injector pulse spark timing and valve timing. Similar to a cylinder leak down test. This leak should be easy to find because it will be making a loud hissing noise. Ideally it should be on the manifold or below the base of the carburetor.

A vacuum leak is downstream of the device. So by doing a vacuum test in just 3 5 minutes you can know if an engine is healthy or not. The engine should snap right back to a steady 17 21 hg vacuum. Start the car and listen for a hissing sound.

The simplest to perform is the running vacuum test. Try to pinpoint where the hissing noise is coming from. Even a tiny leak as small as 0 020 of an inch can degrade engine performance compromise driveability and turn on your check engine light. If there is a vacuum leak the ecm may be unable to compensate.

Steady low between 5 10 hg vacuum. To begin start the engine and let it run until it has reached normal operating temperature. Check engine light.