Operation

Primary control of the system is through the PCV valve. The PCV valve controls the flow rate of the blow-by gases based on intake manifold vacuum. The PCV valve maintains a low flow rate when intake manifold vacuum is high (i.e. deceleration, low speed driving, or idle). The PCV allows a higher flow rate to compensate for increased blow-by when the intake vacuum is low (i.e. acceleration, or high load operation). It abnormal conditions arise, the PCV system allows excessive amounts of blow-by gases to flow through the fresh air tube, and the throttle body to be consumed in the combustion process.