A Positive Crankcase Ventilation (PCV) system is used on all Toyota gasoline engines. Exhaust blow-by gasses 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 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 gasses entering the mixture is also regulated by the PCV valve, which is spring loaded and has a variable orifice.
The components of the PCV system consist of the following:
Inspect the PCV system hoses and connections at each tune-up and replace any deteriorated hoses. Check the PCV valve at every tune-up and replace it at 30,000 mile (48,000 km) intervals. The PCV system is easily checked with the engine running at normal idle speed (warmed up).
- Remove the PCV valve from the valve cover or intake manifold, but leave it connected to its hose.
- Start the engine.
- Place your thumb over the end of the valve to check for vacuum. If there is no vacuum, check for plugged hoses or ports. If these are open, the valve is faulty.
- With the engine OFF , remove the valve completely. Shake it end-to-end, listening for the rattle of the needle inside the valve. If no rattle is heard, the needle is jammed (probably due to oil sludge) and the valve should be replaced.
- Blow air from the cylinder head side of the PCV valve. It should flow easily. Air should pass with difficulty from the manifold side.
When replacing a PCV valve you must use the correct one for the engine. Many valves look alike on the outside, but have different mechanical values. Putting the incorrect valve on a vehicle can cause driveability problems.
- Pull the PCV valve from the valve cover.
- Remove the hose from the valve.
- Check the valve for proper operation. While the valve is removed, the hoses should be checked for splits, kinks and blockages. Check the vacuum port (that the hoses connect to) for any clogging.
- Inspect the rubber grommet the PCV valve fits into. If it is in any way deteriorated or oil soaked, replace it.
- Insert a new valve into the hose.
- Push the valve into the rubber grommet. Make sure the valve is firmly into place.