What is the initial step in a two-stage tailpipe test?

The initial step in a two-stage tailpipe test involves conducting an idle test. This phase assesses the emissions produced by the vehicle while it is idling, allowing inspectors to measure pollutants emitted during a low-load condition. The idle test is vital because it helps identify vehicles that may have issues at low engine speeds, which can often indicate underlying mechanical problems or inefficiencies affecting emissions.

The idle test is essential for establishing a baseline of emissions performance before moving on to the high RPM test in the second stage, which checks emissions under more demanding conditions. Other processes, such as visual inspections or scan tool reviews, serve different purposes in a complete emissions evaluation but do not form the starting point of the tailpipe test sequence.