How does the TAC system affect hydrocarbon levels during engine cranking?

The correct choice highlights that the TAC (Temperature Activated Component) system helps decrease hydrocarbon levels during engine cranking when warm air is introduced. The TAC system is designed to optimize combustion conditions by adjusting the air-fuel mixture and other parameters based on the temperature of the incoming air.

When warm air is used during engine cranking, it helps improve the combustion process. Warmer air is less dense and allows for a more efficient burn of the fuel, leading to a reduction in unburned hydrocarbons, which are a significant component of emissions. This efficiency means that the engine can ignite the fuel-air mixture more effectively, resulting in lower hydrocarbon levels during the critical cranking phase of engine operation.

Conversely, cold air can lead to a richer fuel mixture because cold air is denser, which can increase hydrocarbon emissions. When air is at a lower temperature, the combustion process can become less efficient, resulting in higher levels of unburned hydrocarbons being emitted.

Understanding how temperature influences hydrocarbon emissions is crucial for grasping the overall functionality of emission control systems. The TAC system's role in managing this relationship underscores its importance in smog repair and emissions reduction strategies.