03 cavalier 2.2 Ecotec engine.

So I've been having this problem lately with the car running rough, hesitation, and stalling at idle. Another thing that I noticed was that sometimes when the car runs for awhile when I shut it off there will be a hissing noise coming from the engine compartment that sounds like pressure equalizing (I don't use the AC so it's not that).

Decided to take a closer look at the PCV system and after research I found that there is no PCV valve on this engine. I still removed the intake plenum components and made sure there was no clog in the hose or the system. I'm really starting to think (and praying that I'm wrong) that I'm getting piston ring blowby. When I remove the oil filler cap and the car is running, there is pressure coming out like a little exhaust. I'm assuming this is far from normal.

Any experience with any of this?

Do a compression test to check your theory.

i am having the same problem but when i remove my oil cap i have oil splattering up and exhaust. so i would assume that i really have blow by and that is ok cause i have another motor in my shop floor just im lazy and hate to put it in. i have the 2.2l sfi motor, (the crappy one).