Could My Pcv Valve Be The Cause Of My Idle Issue On My 1995 Mazda Protege?

I have been having idle problems with my 1995 Mazda Protege LX. When I start her cold the idle is really high. When I reach my destiniation the idle seems to lower almost to where she should be BUT when I come back out to start her the idle is really too low, like 0 RPMs low. I checked in my service manual and troubleshooting on Autozone.com and they say it could be my PCV valve. I have never changed it as its always rattles when you inspect it but it's been on there for 14 years, when I bought the car from a dealership. So my question is, should I replace it and will this fix my problem or do I need to dig deeper?