Chevrolet Sonic manuals

Chevrolet Sonic Repair Manual: Crankcase Ventilation System Inspection/Diagnosis

Chevrolet Sonic Repair Manual / Powertrain / Engine / Emissions / PCV / Crankcase Ventilation System Inspection/Diagnosis

Results of Incorrect Operation

A plugged positive crankcase ventilation (PCV) orifice or hose may cause the following conditions:

  • Rough idle
  • Stalling or slow idle speed
  • Oil leaks
  • Oil in the throttle body
  • Sludge in the engine
Functional Check

With these systems, any blow-by in excess of the system capacity, from a badly worn engine, sustained heavy load, etc., is exhausted into the throttle body and is drawn into the engine.

Proper operation of the crankcase ventilation system depends upon a sealed engine. If oil slugging or dilution is noted and the crankcase ventilation system is functioning properly, check the engine for a possible cause. Correct any problems.

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

  1. Remove the PCV hose from the cylinder head cover.
  2. Operate the engine at idle.
  3. Place your thumb over the end of the hose in order to check for a vacuum. If there is no vacuum at the hose, inspect for the following items:
  • Plugged hoses
  • The manifold port
  • Turn OFF the engine.
  • Inspect the PCV orifice in the cylinder head cover for debris or blockage.
  • PCV
    ...

    Positive Crankcase Ventilation Hose/Pipe/Tube Replacement
    Removal Procedure Remove the air cleaner outlet duct. Refer to Air Cleaner Outlet Duct Replacement. Open the 2 positive crankcase ventilation pipe retainer clips ...

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