PCV valve

[Ardent]

So as not to hi-jack https://www.mr2roc.org/index.php?msg=903504

@Carolyn
"The PCV valve on the cam cover does get tired over time and needs replacing.  It is a little more than just a 'non return valve' and the spring tension is critical for it to function properly. Even if it appears to work off the car, it can be past its sell-by date. Toyota recommend replacement every 30,000 miles. Search for it by engine type (1ZZ FE) as opposed to car model.  Look for Toyota 1ZZ PCV valve."

I bought one quite some time ago. When I removed the old and compared to the new, the spring tension appeared the same. I think I put the old one back on. The stand out for me was the spring tension was minimal. A flatulent mouse would be enough to compress it.

Now curious as to what it's roll is.
Venting, emissions control, other breathing function. Not an electronically controlled valve, just air pressure. But with such a light spring almost any pressure would seem to be enough.

Jase the curious.

[MartynMR2]

Ventilation of crank case pressure..though regular oil changes will aid that...same as fuel tank ventilation... basically taking vapour off the tank and recycling it into the combustion process...
As far as I'm aware it's quite a passive process, unlike modern Volkswagens/ VAG based vehicles where engine breathing is quite critical to engine processes