Checking PCV Valve Function (Except 2.5L)

WARNING: This page does not describe the selected car, but rather 35 other vehicles, including the 1992 Pontiac Trans Sport, 1992 Oldsmobile Silhouette, 1992 Oldsmobile Bravada, 1992 GMC Yukon, and 1992 GMC Vandura Special. However, it is still accessible from the selected car via links, so may be relevant.

Remove PCV valve from rocker cover. Run engine at idle. Place thumb over open end of valve to check for vacuum. If there is no vacuum at valve, check for obstruction in manifold port, hoses or PCV valve. Repair or replace as necessary.
Turn engine off. Remove PCV valve. Shake valve and listen for rattle of check valve inside PCV valve. If a clear rattle is not heard, replace PCV valve.
Visually inspect valve for varnish or deposits that may make PCV valve operation sticky, restricted or incompletely seated. Replace if necessary.
An engine must be sealed for the PCV system to function as designed. If leakage, sludging or dilution of oil is noted and the PCV system is functioning properly, check engine for cause, and repair as required to ensure PCV system will continue to function properly.
Since an engine operating without any crankcase ventilation can be damaged, it is important to replace PCV valve and air cleaner breather at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

NOTE: The 2.5L engine does not use a conventional PCV valve. Valve consists of a fixed restricted orifice. To test valve, simply check for presence of vacuum with crankcase vent tube inlet end removed from rocker cover and engine running.