The only thing I have to go on is that I just replaced the PCV valve recently and it seems to be pretty sticky already. Having a hard time finding an air filter for the Kia out here in the sticks... Part 2 -- I would guess that an abnormally high PCV draw would funk up the intake quicker as well?
Could it contribute to a rough idle - especially with A/C on?
See IndyLan's post. The throttle plate is 10,000 times more restriction at idle than the dirtiest air filter imaginable. If the air filter could actually be clogged enough to affect idle AT ALL, that would mean that it has become more restrictive than a closed throttle plate and thus the engine wouldn't even run at any speed above idle.
Any increased PCV flow would be small & negligible. Per 440Magnum's point, I'm pondering the effect of a dirty air filter on PCV flow in an engine that doesn't have a throttle. (BMW has no throttle butterfly.)
Bmw no butterfly?????? Really!!!!!
My wife's dd is an 09 328i and it has a huge butterfly valve. I know because i've cleaned it.
Unless your talking diesel, but any diesel from 04+ has a butterfly valve to work with the egr system.
Does it matter that I was wondering if the increased PCV flow would affect idle, not the air filter?
Depends on some specifics of the vehicle. If its a speed-density system that goes into closed-loop mode at idle, then excessive PCV flow will tend to lower MAP, raise the idle speed, and the IAC will close up to compensate, but overall the mixture should remain correct and I wouldn't expect much change in idle quality. If its a mass-airflow system or any system that stays open-loop at idle, then excessive PCV flow will look like a vacuum leak and tend to lean things out, potentially causing idle issues.
The BMW engines with variable-lift valves ("Valvetronic," I think) use the intake valve lift/duration instead of a throttle butterfly to control engine speed. The end result is a lot like Fiat/Chrysler Multi-Air, though the implementation is completely different.