[tdangle]

Originally Posted by weq92f

Well... it depends...

The PCV valve is supposed to restrict air flow under high vacuum ( idle ) conditions down to something small enough not to affect idle quality. That is, the controlled vacuum leak that is the PCV system is supposed to go away at idle.

If the PCV valve you have currently isn't doing that, then you have too large a vacuum "leak" at idle as a result, which will cause the things that vacuum leaks cause!

Easy enough to check. Before I recently replaced my non-functioning-properly PCV valve, plugging the vacuum line to it caused idle to clean up very nicely ( just as if a vacuum leak had been plugged ) and likely did increase overall Hg as well!

-klb

It just hit me how the dumb thing works! Always wondered how and was always told shake it. If it rattles it's OK. Now I understand at high vac such as cruise or idle the weight (or what ever it is) pulls up and pretty much closes off the sucking from the engine/valve cover. At lower vac levels the weight drops and the engine can pull vapors from the engine. What a simple design!