Contents: Action ⇊ Testing and troubleshooting ⇊
Action
A closed crankcase ventilation system is used on all HONDA vehicles. This system returns unburned fuel (i.e., fuel that has leaked past the piston rings) to the intake manifold for combustion along with the air-fuel mixture. The oil cap is sealed, and air is released from the top of the crankcase into the intake manifold through a shut-off valve.
This valve (PCV valve) regulates the flow of air into the manifold depending on the vacuum in the manifold. When the throttle is wide open, the PCV opens to maximize flow, but at idle, when the suction action of the manifold is at its maximum, the PCV valve reduces flow because the need to recirculate the mixture entering the engine is reduced. The recirculation system depends on the tightness of its connections. An air leak anywhere: the valve cover, the cylinder head gasket, the oil pan, the dipstick location, the air collector passages in the oil cup cap or vacuum hoses can lead to an air-saturated air-fuel mixture and reduce the effectiveness of recirculation. And an incorrectly connected hose will cause the manifold to fill with oil, stall the engine and / or leak oil.
Testing and troubleshooting
The PCV valve is easily tested by running the engine in normal idle mode (warm-up mode). Lightly press your finger on the open end of the valve. You should hear a whistling sound. If there is no whistling sound, remove the valve from the valve cover or separators, place your finger on the open end of the valve. You should hear a whistling sound and feel a vacuum.
If there is no vacuum, check the connected hoses and connections. If they are open, the valve is faulty. With the engine off, remove the valve completely. Shake it to listen for a rattling sound from the plunger inside the valve. If there is no rattling, the plunger is stuck (probably due to oil buildup) and the valve should be replaced. Never operate the engine without the PCV or with a clogged hose.
DO NOT attempt to blow out the valve: gasoline vapors and deposits on the valve are harmful to health.
(The original is located on the website «HONDABOOK»)