A vehicle smoke test, also known as an air leak test, is a diagnostic procedure used to identify air leaks in a vehicle's engine or exhaust system. This test is typically performed by a trained technician using specialized equipment, and can help to identify a variety of issues that can affect the performance and reliability of a vehicle.

During a smoke test, the technician will introduce a small amount of smoke into the engine or exhaust system. The smoke is typically generated using a machine that produces a safe, non-toxic smoke that can be easily seen in bright sunlight. The technician will then observe the smoke as it travels through the system, looking for any signs of leaks or other issues.

Common areas where air leaks may occur include the intake manifold, vacuum hoses, exhaust system, and various sensors and valves throughout the engine compartment. By identifying these leaks and other issues, the technician can help to diagnose and repair problems that may be affecting the vehicle's performance and reliability.

Smoke testing is a valuable tool for diagnosing a wide range of issues, from minor air leaks that can affect fuel efficiency and performance, to more serious issues such as exhaust leaks that can create safety hazards for the driver and passengers. By identifying and repairing these issues early, vehicle owners can help to ensure the long-term reliability and safety of their vehicle.