PCV Valve - Who Knew?

[Merlin]

It seems that a few of the little issues on my 5th gen seem to be caused by a blocked PCV valve. Recently my 5G has been idling low, had a hesitation between 2 & 3K rpm and sometimes gave a IAT sensor CEL.

The other night I went to adjust my idle to compensate (get engine up to temp, remove IACV electrical connector and adjust idle screw). But I think the threaded hole for the screw was a little corroded so we couldn't adjust it much. At the time I heard squealing from the engine and traced it to the PCV valve. Removing the valve from the top of the engine stopped the squeal. We removed the valve and hose and cleaned it out.

Now the car idles fine, I have not yet had re-occurrence of the hesitation, and the engine generally seems a bit perkier (could just be me though).

The service manual does state that the PCV system should be examined before adjusting idle but I didn't read that but until after .

Some info about what the PCV does, most of which I did not know http://www.agcoauto.com/content/news/p2_articleid/197

Anyway all sorted now

[Lude-dude]

wow simple fix

good job

[wurlycorner]

I knew!*



* I didn't really

[hoppi05]

We're is the pvc valve on the h22 whilst I have the engine out I may as well double check if I cleaned this originally

[JEBB4]

Good bit of info on that system, many people say that smoke on VTEC can be caused by blocked PCV valve which would make sense..
I think I'll have a look at mine, is it the red one between rocker and inlet??

[Merlin]

Yeah it is on the top of the rocker cover on the rear right hand side.

Hard to believe that the little valve can have such a big impact. Helping to regulate idle, IM vacuum, and effects intake temps.

[vanzep]

hmmm - ive changed my one over before with a better condition part from a breaker and i have cleaned the pcv valve once or twice with carb cleaner - i thought it just was a pressure release valve for the head that vented into the intake mani.
Had no idea it made such a difference as you are saying

[lewd lude lover]

Recent learning has shown that blocked or even partially restricted PCV can and will cause main oil seals to blow out premature and all kinds of other basic problems.


Not as obvious or as dangerous on petrol as diesel due to the compression ratio difference but still, having a positive pressure inside the engine seems to be a bad thing all round.

Kinda like a blocked bile duct in a human maybe... not a major part, just a part of a bigger system. But when its not working right the whole system starts to run rough and eventually suffers major failure because of it.

[NafemanNathan]

having a positive pressure inside the engine seems to be a bad thing all round.

Ratty's going to love this, but...

Is this more reason to have a breather filter on the valve cover (air intake pipe side) and do away with the OEM connection to the air intake pipe? There'd be no additional air being blasted into the head to maintaining a constant pressure, and if ever the PCV did get blocked, at least the gases will find it easier to past back out through the breather filter instead.

Or!... Is the constant filtered air that's being blasted into the head via the air intake pipe connection, mixing with the gases and allowing a less contaminated vapour to escape through the PCV, making it less likely that the PCV will clogg up in the first place?

[vanzep]

good question
who is going to be brave enough to answer that one