The complete lack of coverage on Vacuum gauges and their importance ....it isnt our fault ........changing times have prompted us to rely more on OBD scanners to diagnose engine problems where most of us forgot that the engine sitting nicely under our hood was still a hundred year old piece of marvel ......and before the days of the computer wizardry .......a competent mechanic using nothing more than your spark plug (colour) , compression tester and the vacuum gauge could track over a number of engine performance related issues today we will focus and talk about Vaccum gauges and how to use them....... Word of advice : Invest in one (buy one) Vacuum Gauge Though little understood, the vacuum gauge is probably the best single indicator of your engine's health you can get. When your car is idling-whether it's fuel injected or carbureted-the throttle plate or plates are restricting the amount of air the engine can breathe in. The pistons are attempting to ...