GM Service Manual Online
For 1990-2009 cars only

Crankcase Ventilation (CV) System Inspection

    • Test for vacuum at the positive crankcase ventilation (PCV) dirty air hose where it connects to the vacuum orifice tube in the engine valley cover. There should be a manifold vacuum present at the hose. If there is no vacuum, inspect for a plugged hose, leaking hose or a plugged intake manifold passage.
    • If oil has accumulated in the intake , inspect for the following conditions:
       - Plugged vacuum orifice tube in the engine valley cover
       - Plugged, restricted, or leaking PCV dirty air hose
       - Plugged or restricted intake manifold passage
       - Excessive crankcase pressure or blow-by
    • Additional items to inspect:
       - Plugged or restricted PCV fresh air hose
       - Inspect the valve rocker arm cover, the oil pan, engine front cover, and other sealing areas for leaks

Results of Incorrect Operation

A plugged crankcase ventilation system may contribute to the following conditions:

    • A rough idle
    • Stalling or a slow idle speed
    • Oil leaks
    • Oil accumulation in the intake manifold
    • Sludge in the engine

A leaking hose may contribute to the following conditions:

    • A rough idle
    • Stalling
    • Unstable idle speed

The crankcase ventilation system has no serviceable components so no maintenance of the system is required.