Strong vacuum at oil fill port... PCV issue?

97 Grand Prix GT (K) with 130k miles all stock except for K&N air filter

Changed the PCV about 2 weeks ago and recently noticed that something wasn't right with the car... Took the oil fill cap off while the engine was running and noticed SUPER vacuum such that the car stalled when I opened it... I see no obvious issues with the vacuum lines and the PCV seems fine. Do I have a MAP issue or some other sensor? Must be a vacuum issue!!! Help!!! Anyone ever see this?

This guy did, but this engine was had lots of mods: http://www.clubgp.com/newforum/tm.asp?m=2844909

Thanks!

How about both o-ring seals? Check the small black one for the PCV valve and the big orange one that seals the plastic MAP retainer to the UIM?

Sure enough....

The PCV o-ring was missing... I'm a dope and you guys on this forum are gurus!

Thanks again!

Glad it's fixed, and don't beat yourself up too much. It's a fairly common issue. That o-ring is easy to miss, especially if you don't know it's there.

You are welcome. Important thing you you got it fixed without having to waste money. We've all been through the school of hard knocks on our Grand Prixs.

BTW - Those guys at GlubGP do the hard things first and the easy last. :dunno: