A specific question about the old "dipstick popping out" issue

[Huskymaniac]

So I noticed one day that the dipstick was out. I pushed back in and drove the car a few times and it didn't pop out. After a couple of weeks, it was out again. I noticed it when I went to work on the hood squeak.

I know the two issues are the rubber o-ring and the PCV valve. I know that a new o-ring usually solves the problem. My concern is what if it is the PCV valve? Getting a better seal on that dipstick would only cause the pressures to rise and there might not be any other immediate symptoms of a stuck PCV valve. Assuming that were the case, what damage could be done by not replacing a bad PCV because either one doesn't know about it or one saw a symptom but fixed that symptom another way and assumed the PCV valve was OK?

Normally I would just replace the o-ring and not worry too much about it but I have another symptom that might point to the PCV valve in an indirect way. When the weather got cold my idle would bounce immediately after starting the car. It would jump up to a normal RPM first. Then it would drop very low and nearly stall. Then it would bounce back to the normal cold RPM again. Then it would drop again but not as low. This repeats and the "undershoot" is less each time until the car finally settles on the normal RPM for a cold idle. It takes all of about 5 seconds for this to happen.

From what I have read, it sounds like this could be due to a stuck AACV and the AACV could be stuck due to oil being pushed out which in turn could be due to the stuck PCV valve. However, this bouncy idle seems to be getting better with time since I replaced the O2 sensor. Sometimes it doesn't bounce at all. Maybe the AACV is OK and the bouncy idle was due to the O2 sensor. And the underside of the car looks pretty dry right now. I get zero drips of oil on the driveway. So maybe the PCV isn't stuck after all.

But the bottom line is, what damage can be done by a stuck PCV valve?