A positive crankcase ventilation (PCV) system is used on all Toyota gasoline engines vehicles sold in the United States. Exhaust blow-by gases are routed from the crankcase to the intake manifold, where they are combined with the fuel/air mixture and burned during combustion. This reduces the amount of hydrocarbons emitted by the exhaust.
A valve (PCV) is used in the line to prevent the gases in the crankcase from being ignited in case of a backfire. The amount of blow-by gases entering the mixture is also regulated by the PCV valve, which is spring loaded and has a variable orifice.
The important components of the PCV system are:
PCV system service is relative easy, as it consists of making sure that the PCV valve is working and that all the hoses and connection are tight and in good shape. A clogged PCV valve and/or restricted hoses can cause the engine to run poorly.
Check the attaching hoses for cracks or clogs by visually and physically inspecting them. Check the PCV system hoses and connections to ensure that there are no leaks, then replace or tighten, as necessary.
To check the valve, remove it and blow through both of its ends. When blowing from the side which goes toward the intake manifold, very little air should pass through. When blowing from the crankcase (valve cover) side, air should pass through freely.
Replace the valve with a new one, if the valve fails to function as outlined.
REMOVAL & INSTALLATION
Remove the PCV valve from the cylinder head cover or from the manifold-to-crankcase hose by unthreading or pulling out. Install by reversing the removal procedure.