Intake manifold vacuum is a key indicator of engine performance.
By measuring vacuum under different engine loads and conditions, you can track down problems within your engine and make the necessary adjustments or repairs. The key is having a reliable engine vacuum gauge and then knowing how to read it properly.
We’ve said it before, but an engine vacuum gauge is an extremely valuable tool. It’s so valuable, in fact, that OnAllCylinders contributor Lori Sams put together this visual cheat sheet to help you understand common gauge readings.