The only way I can answer those questions would be to explain how the PCV works.
Positive Crankcase Ventilation Valve: PCV Valve
On a VX...if the valve is rattling when you shake it that means it is good. This is because it is acting like a simple ball & check Valve. If it is not rattling than it is stuck either open or closed.
In a normally operating PCV System...the pressure in the crankcase has to go somewhere and it is looking for the least path of resistance, which in this case is the valve, which gets popped off its seat (lifted up by the pressure) as it allows the pressure to escape through the exit hose back to the intake. It is sent back to the cylinders for reburning as this pressure is considered a contaminent in that by-products of the combustion process are mixed in the air being released.
As this pressure begins to release you get a "Venturi effect" in that air begins to circulate the crankcase because it is now being pulled into the left valve cover (opposite the right valve cover with the PCV Valve) which on a stock VX has a hose that goes to your air filter box IIRC; as mine is no longer stock since I simply have a breather filter installed on the left valve cover. Either way...filtered air is now being sucked into the left valve cover and "postively ventilates the crankcase" as the valve allows it to exit the right valve cover.
On pre-emissions controlled cars they simply installed a breather pipe that dropped down below the engine block and vented the pressure out to the atmosphere. This is why you could bypass it with a breather filter as someone above has shown. This will not pass emission testing however.
If your PCV Valve is faulty in that it no longer rattles when shook. That means the valve is either stuck open or stuck closed. Stuck open would be preferable as this would be like the "gutted PCV" someone mentioned above and simply always release pressure...but for some reason...mine only knows to get stuck closed which is not preferable in that pressure now builds up in the crankcase and is looking for another way to release....more than likely it will cause the PCV system to sort of work in reverse in that the pressure will now exit the left valve cover and probably foam oil spray towards your air filter box via the hose on a stock VX or in my case out the breather cap.
On other vehicles it has been known to blow the oil pan off the engine block in severe cases...usually though it caused the oil pan gasket to start leaking as pressure escaped.
There is no code thrown for any of the above so your VX's computer won't pick up on this.
A popular theory that has been mentioned here on this site is that if your PCV sticks closed and pressure builds up in the crankcase...this pressure resists your oil returning back to the oil pan which means it stays longer up in the cylinders which results in higher burn-off. Add to this, if your EGR Valve is faulty it is stuck closed as though you "blocked it off" and results in higher cylinder temps. Combine the two faults and now you have oil lingering longer in what is now hotter operating cylinders which is the perfect storm for oil burn-off hence greater consumption of oil.
I had previously purposely blocked my EGR with a blocking plate when my EGR went bad as I didn't want to spend the $$$ to replace it and by blocking it off you raise the cylinder temps supposedly gaining performance since only pure air/fuel is going in and not reburnt exhaust too. However, I noticed worse oil consumption especially when my PCV would stick closed too. I've since un-blocked the EGR and replaced it with a new one and as I've said before...I check my PCV after every fill-up when I'm under the hood checking my oil level too. If my PCV isn't rattling..I used either a spurt of SeaFoam or PB blaster to free it up until I can find a GOOD, Quality PCV Valve!!!!!!!!!!!
Sorry for the long-winded post...hope it helps! Gotta go to work! Bye! lol.
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