Location of the crankcase ventilation valve on 4-cylinder models
The valve is located on the valve cover.
1. Start and warm up the engine.
2. Remove the valve from the valve cover. Close the valve with your finger. If there is no vacuum, check to see if the hose, the hole in the intake manifold, or the valve itself is clogged.
3. Turn off the engine. Shake the valve. You should hear the plunger tapping inside the valve. If not, replace the valve.
For details, see the website (mazbook)