Why is it important for a vehicle to be warmed up before an emissions test?

Warming up a vehicle before an emissions test is crucial because a warm engine operates under optimal conditions, leading to more accurate emissions results. When the engine is cold, it doesn't reach its ideal operating temperature, which can result in incomplete combustion of fuel. This incomplete combustion leads to higher levels of harmful emissions, giving misleading indications of the vehicle's environmental performance. A warm engine, on the other hand, ensures that the catalytic converter and other emissions control systems are functioning effectively, ultimately providing a true representation of the vehicle's emissions levels during the test.

This understanding highlights the importance of proper testing conditions to evaluate a vehicle's compliance with emissions standards accurately.