1. How to check?
For car owners, daily inspections mainly rely on observation and perception:
Observe the oil dipstick: Check if the engine oil is abnormally consumed too quickly or if there is a gasoline smell or water droplets.
Listen to the sound of the engine running: whether there is an irregular "hissing" sound (possibly due to vacuum leakage) or weak acceleration when idling.
Check for oil leakage: whether there are traces of fresh oil leakage on the outside of the engine, around the valve cover, and at the oil seal.
Reading OBD fault codes: If the instrument panel engine fault light is on, the diagnostic computer can be used to read the fault codes. P0171 (system lean), P0300 (random/multi cylinder misfire), etc. are sometimes related to PCV system problems.
For professionals or car owners with strong hands-on abilities:
Check PCV valve: Use pliers to clamp the vacuum pipe connecting the PCV valve while the engine is idling. If there is no significant decrease or change in engine speed, it indicates that the PCV valve may be malfunctioning (normally open). Or remove the PCV valve and shake it for testing. There should be a crisp "dada" sound, and there may be no sound or the sound may be dull and stuck.
Check the filter: If the vehicle is equipped with an independent replaceable filter, it can be disassembled for observation. The surface of the filter element should be relatively clean, without serious oil sludge or blockages. If it turns black, greasy, or clogged, it must be replaced.

2. How to replace it?
The replacement of PCV valve and ventilation filter is usually carried out synchronously.

Search for information: Find the specific location of your vehicle's PCV valve and filter through the repair manual or reliable resources (such as iCar, Alfa Romeo Forum, etc.). The PCV valve is usually inserted into the intake manifold and connected to a pipe leading to the valve cover; The filter may be inside the valve cover or in the pipeline.
Preparation tools: Usually only a wrench and screwdriver are needed, some models may require an Allen wrench.
Disassembly and installation: Remove the vacuum tube and unscrew the old PCV valve; Remove the old filter. Install new parts in reverse order, paying attention to torque (especially plastic parts, do not twist them) and sealing rings (if any).
Start up inspection: After installation, start the engine and check for any vacuum leakage sounds. Observe whether the idle speed is stable and whether the fault light is off.