You have a black o-ring that goes around the PCV valve and seals it in its bore. This o-ring can stay in the bore when the valve is removed and is hard to see, black on black. Without this o-ring you will have vacuum in the motor at idle. Remove the oil filler cap crank the car and put your hand over the hole. If your hand is held to the valve cover the “black” PCV valve o-ring is missing or needs replacing.
When the o-ring is in place around the PCV valve it fits tightly in its bore. If you can remove or install your PCV valve easily with your fingers the o-ring is missing or needs replacing.
L36 PCV valve kit comes with PCV-892C valve, black and large orange o-ring, spring and plastic cap.
Part # 89017274. $18. Dealer $11. Delco
Stock 96 Regal 3800 II