Answer :
Final answer:
At idle, the high engine manifold vacuum causes the PCV valve to be open, allowing vapor flow back into the intake system. This process helps reduce emissions by recirculating crankcase vapors. Understanding this function is crucial for efficient engine performance.
Explanation:
Understanding the PCV Valve Functionality
The Positive Crankcase Ventilation (PCV) system plays a crucial role in controlling engine emissions by allowing gases that escape from the combustion chamber to be reintroduced back into the intake manifold or sent to other systems. When an engine is idling, it creates high manifold vacuum, affecting the functionality of the PCV valve. The plunger inside the PCV valve responds to changes in manifold pressure and regulates vapor flow accordingly.
Analyzing the Options
During idle, when the manifold vacuum is high, the PCV valve works as follows:
- A) Sealed allowing vapors to be emitted to the atmosphere - Incorrect, as it contradicts the purpose of the PCV system.
- B) Closed diverting vapors to the EVAP system - Mostly incorrect, as EVAP systems handle fuel vapor.
- C) Open allowing vapor flow - Correct, as the PCV opens when manifold pressure drops allowing vapor to flow back into the intake.
- D) Sealed restricting vapor flow - Incorrect, as that would negate the function of the PCV valve intended to reduce emissions.
Therefore, the correct answer is C) open allowing vapor flow, as this enhances combustion efficiency and minimizes harmful emissions.
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