A positive crankcase ventilation system is used on all Toyota engines sold in the United States. Blow-by gases are routed from the crankcase to the intake manifold, where they are combined with the air/fuel charge and burned in the combustion process. On fuel injected engines, a pair of fixed orifices in the PCV line regulates the blow-by flow.
Every 30,000 miles, the PCV system should be checked for tight hose connections, leaks, cracks or deterioration. Any hoses found to be leaking should be replaced. To check the PCV valve operation, remove the valve from the valve cover and blow through both ends. When blowing from the intake manifold side, very little air should pass through the valve. When blowing from the crankcase (valve cover) side, air should pass through freely. If the valve fails either of these tests, it should be replaced. Do not attempt to clean the PCV valve. Simply clean the calibrated orifices with solvent and blow dry with compressed air.