GM Service Manual Online
For 1990-2009 cars only

Positive Crankcase Ventilation (PCV) System Inspection

    • Test for vacuum while the engine is running at the foul air tube where it connects to the right side camshaft cover positive crankcase ventilation (PCV) orifice fitting. There should be manifold vacuum present at the tube connector. If there is no vacuum, inspect for a plugged tube or connector, leaking tube or connector, or a plugged supercharger PCV fitting.
    • Plug the end of the foul air PCV tube while the engine is running. Inspect the tube for any areas that collapse when the end of the tube is blocked. Replace the PCV tube if it collapses when blocked.
    • If oil has accumulated in the intake air duct, inspect for the following conditions:
       - Plugged PCV orifice in the right side camshaft cover PCV fitting
       - Plugged or restricted PCV fitting on the supercharger
       - Excessive crankcase pressure or blow-by, refer to Oil Consumption Diagnosis .
    • Additional items to inspect:
       - Plugged or leaking fresh air PCV tube
       - Plugged or restricted passages in the air duct
       - Missing or damaged PCV tube connectors
       - Inspect the cam covers, the oil pan gasket, and other sealing areas for leaks

Results of Incorrect Operation

    • A plugged PCV orifice fitting or PCV foul air tube may contribute to the following conditions:
       - A rough idle
       - Stalling or a slow idle speed
       - Oil leaks
       - Oil accumulation in the intake air duct
       - Sludge in the engine
    • A leaking PCV fresh air tube may contribute to the following conditions:
       - A rough idle
       - Stalling
       - Unstable idle speed