Replacing the PCV Valve

While an engine is running, a small amount of the combustion gases leaks past the piston rings into the crankcase.  This is commonly referred to as blow-by.  The crankcase ventilation system directs crankcase vapors back into intake manifold to be consumed in the combustion process instead of allowing it to escape into the atmosphere.  This is controlled by the PCV valve.  For some reason, in the service manual this valve is called the PCV valve in the section dealing with the 3.4L engine while it is called the crankcase ventilation valve in the 3.8L engine section.  I am going to use PCV valve just for consistancy.

The first part of this article is for the 3.8L engine.  Dan send me photos for the 3.4L engine and it is located where I would expect it, in the valve cover.  Scroll down the page for his photos.

Credit for this article goes to Mattmcdill and 00Impala from Edmunds.  They wrote the article, I just took photos.

3.8 L Engine
Where the *%#@^!! is the PCV valve?!?!  I am used to it being in a valve cover.  Turns out it is under this cap.  Strangely enough, there is an electrical harness attached to it, which is why I would have never figured out that it was under there without Matt pointing it out.
To get the cap off, you need to remove the fuel injector sight shield (how does Chevy come up with these names??).  Clean the area around the oil fill cap and extension tube to prevent things from falling into the engine.  Twist the oil fill cap counterclockwise and remove it.  Do the same for the tube.  You don't have to remove the cap from the tube, it was just easier to grab onto the tube with the cap off.  Again, carefully clean the area to prevent stuff from falling in.
This is what the oil fill cap and extension tube looks like.
The shield is held into place by the extension tube and a tab that goes into a hole in an engine bracket mounted near the firewall.  Watch out, there is a rubber cap on this tab and it can come off and fall into the engine bay and you'll never find it again.
This is what the rubber cover looks like just before it falls off into the engine compartment.  Just push it back on.
Here is the "fuel injector sight shield."  Put the oil cap and extension tube back into the valve cover.
The PCV valve is under this cap.  It is located on the passenger side of the engine.  That is the alternator on the left side of this photo.
Remove the electrical connector by lifting up the tab and gently pulling.  The arrow is pointing to the removed connector.  Then gently push down and turn the cap counterclockwise.  It is spring loaded and is similar to a radiator cap.
Here is the PCV valve attached to the cover.  Notice there is a black o-ring on the bottom of the valve.
The valve may not come out with the cap.  This is what you would see if this happens.
This is what the whole thing looks like when you take it apart.  Inspect the o-ring for damage and replace if required.
There is another o-ring for the seating surface of the cap.  There may be a lot of debris around the o-ring.

Carefully clean this area and remove the o-ring.  Make sure nothing falls into the engine.  Inspect the o-ring for damage.  Replace as required.
Here is a close up view of the o-ring.

To reinstall, just reverse the process.  Don't forget the two o-rings and the electrical connector.

3.4 L Engine
These are Dan's photos of a 3.4L engine.
The PCV valve is in the valve cover, connected to the intake manifold by a black hose.  This photo was from Jon.
Pull up on the hose an the PCV valve should pop out.  Or the hose may come off the end of the PCV valve, leaving the valve in the valve cover.  Either way, inspect the hose, valve and grommet in the valve cover and replace as required.
Here is a close up view of the PCV valve.

How do you know if the valve may be faulty?  The following is from the service manual (if you don't have the GM service manual, what are you waiting for?  I know it's a lot of money, but it is worth it.  Don't bother with the books you can get from your local auto parts store, they don't go into enough detail and are pretty generic in most areas.):

A plugged valve may cause the following conditions:
A leaking valve would cause:
To check to see if the valve is good, remove the valve and shake it.  You should hear the needle valve rattling.  If you don't, replace the valve.  I know it sounds hokey, but hey, it works.