An automotive smoke machine is a diagnostic tool used to locate vacuum and vapor leaks. Modern engines are highly sensitive to unmetered air entering the intake system, which triggers lean codes and rough idling. Also, EVAP emission systems must be completely sealed to prevent fuel vapors from escaping. Finding a pinhole leak in a labyrinth of rubber hoses under the hood by eye is nearly impossible. The smoke machine solves this by pumping a dense, white mineral oil vapor into the system under low pressure.
Once the system fills with smoke, you look for where the white vapor escapes. The kit usually includes a bright LED light or UV dye to help spot the smoke in dark engine bays. Since the pressure is kept very low (typically under 1 PSI), there is no risk of blowing out seals or gaskets. This tool is the fastest way to find leaks in intake manifolds, vacuum lines, throttle body gaskets, and EVAP canisters.