Need Help with Buick 3.8 in 1997 Lasaber

[JohnBrowning]

I am building a huge vaccum in the heads. The vechile is stumbleing at idle and is running laborered. It astill has awsome performance off idle. Check engine light just came on.

When I remove the oil cap it takes quite a bit of force to remove the cap. The car is generateing a very strong vaccum. As luck would have it my vacuum guage is not working. I have very little experince trouble shooting GM powertrains. Is this normal?

In imports you always have an overpressure in the heads and get positive pressure comeing out of the heads.

I replaced the PCV valve about 7000 miles ago with OEM parts. It will only go in one way so it is not in backwards. I do not have any exhaust gas's in the coolant, no coolant leaking from intake manifold etc....

P.S. No oil consumption either.

 

[GT Mike]

You need that O-ring around the PCV valve to seal it to the upper plenum properly. There's also a spring that forces the PCV valve down tight into the plenum.
A lot of times I see the springs missing, since they're kind of a bear to compress and tighten the MAP sensor bracket back down on the plenum. A little trick is a deep 16mm socket on a 6" extension and ratchet. You can push down evenly then.

 

[GT Mike]

If you need some pics or a more detailed writeup, hit me backchannel at [email protected]
I have the same setup as you do in my '97 Grand Prix GT.

 

[JohnBrowning]

I am working from memory hear but I belive that it had two O-Rings and big spring. I have to admitt it was a B!tch to get it back into the manifold. I will double check to make sure they are selling properly. The spring is in it and the o-rings are their as well! I belive when I put it together I used fresh O-ring supplied by felpro. It might not be seating properly?

Last time I put it in was when I replaced the manifold. I was afraid to remove the map sensor for fear it would break. The OEM map sensor came off in my hand when I tried to remove it to replace the OEM PCV.

Again thanks I will double check the O-rings!! I have to admitt I was trying to ovoid touching that thing as it is a PIA to put the top back on!

 

[GT Mike]

There's only 1 O-ring for the PCV valve...The one that slips around the body of the valve itself. When installed in the plenum, you shouldn't be able to "rock" the valve in its hole much, if at all.

BTW, GM has an updated MAP sensor bracket. It's included with the PCV service kit that retails for ~$15 and includes a new valve, O-ring, spring, plastic tube (that I threw out) for inside the plenum, and a revised (and much stronger) MAP sensor bracket.

If you're interested, I can probably dig the part number up still, as I think I saved the box top somewhere in my toolbox just for this reason.

 

[JohnBrowning]

GT Mike I installed that revised PCV kit 7000 miles ago. I too threw the tube away! When I removed the old pcv it was just sitting in their with no spring. The new kit had the pcv, spring, instruction sheet, o-ring and the top cap and braket combo. No part store in town had the PCV for it so I just got one from GM directly. Thanks though!!! I know that their is one o-ring wear the PCV sits into the manifold. Is their suposed to be one around the cap/map bracket as well?

What problem is associated with not installing the spring? I ask because the origanal did not have a spring in the set up. I installed the spring because the instructions told me too! Is the spring their to keep pcv located in the bore or is it their to preload the cap so vibration does not cause it to lousen up etc......

I sure hope tomorrow I fid it is something simple like I installed an extra o-ring by accident!

 

[JohnBrowning]

GT Mike, You were right on the money yet again!! I had to dig through my collection of o-rings but I found one that would work. I put right were you said their should be one and problem solved.

This is strange because the old one did not have on on it. THe replacement kit did not contain an O-Ring for that location and the new intake manifold wich came with all the gaskets etc... did not have one their either. THe origanal did not have the spring either wich I installed 7000 miles ago with the retro-kit.

Again Thanks. I thought it had to be the PCV but it function fine out of the car. I never would have guessed "O-Ring"! This is were nowing an given engine and it's problems is really a nesesity!!