GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Alero Export 🢒 Engine 🢒 Engine Controls - 3.4L 🢒 Crankcase Ventilation System Diagnosis

Results Of Incorrect Operation
    •  A plugged valve or hose may cause the following conditions:
       -  Rough idle.
       -  Stalling or slow idle speed.
       -  Oil leaks.
       -  Oil in air cleaner.
       -  Sludge in engine.
    •  A leaking crankcase ventilation valve or hose may cause the following conditions:
       -  Rough idle.
       -  Stalling.
       -  High idle speed.

Functional Check

If an engine is idling rough, check for a clogged crankcase ventilation valve, a dirty vent filter, air cleaner element, or plugged hose. Replace as required. Use the following procedure:


    Object Number: 16119 Size: SH
  1. Remove the crankcase ventilation valve from the rocker arm cover.
  2. Operate the engine at idle.
  3. Place your thumb over the end of the valve in order to check for a vacuum. If there is no vacuum at the valve, check for the following items:
    4. •  Plugged hoses.
    •  The manifold port.
    •  The crankcase ventilation valve.
  4. Turn OFF the engine. Remove the crankcase ventilation valve. Shake the valve. Listen for the rattle of the check needle inside of the valve. If valve does not rattle, replace the valve.