What is the purpose of the VSV being in the 'closed' position when the engine is not running?

The purpose of the VSV (Vacuum Switching Valve) being in the 'closed' position when the engine is not running is to avoid a difficult restart condition when warm. In this state, the VSV prevents the intake of undesired air into the intake manifold, which helps maintain proper pressure and prevents backflow. If the VSV were open while the engine is off, it could allow air to enter the system inappropriately, leading to issues such as improper fuel atomization during a restart. This can result in challenges in starting the engine, especially when warm, as it may lead to a lean mixture or insufficient vacuum conditions that are necessary for the engine to start smoothly.

Maintaining the VSV in the closed position when the engine is not operational ensures that the system remains optimally sealed, which is crucial for engine management and performance upon restarting. This function directly contributes to smoother and more reliable engine operation.