Lexus 90999-92002 Hose, Vacuum

Fresh air is drawn from the air filter housing through hoses into the engine's crankcase. This fresh air mixes with blow-by gases and exits through the PCV valve into the intake manifold. During conditions of high intake manifold vacuum, such as idle and part-throttle, blow-by gases flow through the PCV valve and crankcase ventilation hose into the intake manifold. Meanwhile, fresh air is drawn from the air intake duct through the fresh air inlet hose into the crankcase.

The PCV system aims to reduce hydrocarbon emissions by directing blow-by gases and crankcase vapors from the engine's crankcase into the intake manifold. This allows these gases to mix with intake air before entering the combustion chambers for combustion.