GM Metro/Sprint 1985-1993 Repair Guide

PCV Valve System

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OPERATION



See Figure 1



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Fig. Fig. 1: PCV valve system operation

The PCV valve system is designed to force blow-by gases generated in the engine crankcase back into the carburetor or throttle body, then deliver them together with the fuel mixture into the combustion chambers. This system is a closed type and consists of a PCV valve in the cylinder head cover for separating oil particles from blow-by gases and a hose to the carburetor or throttle body. The air cleaner allows fresh air into the system.

Under normal operating conditions blow-by gases passing between the piston rings and fuel vapor from the fuel tank are mixed with the ambient temperature supplies from the air cleaner. This mixture is then drawn through the PCV valve into the intake manifold for burning. When the engine is operating with the throttle wide open, part of the blow-by generated is drawn directly into the air cleaner via a hose in the cylinder head cover.

INSPECTION



The PCV system should be inspected every 60,000 miles (100,000 km). Check the PCV valve for blockage or deterioration. Clean the valve and hoses with carburetor cleaner and dry with compressed air. Check the mounting grommet and hoses for deterioration and leakage; replace as necessary.

PCV Valve
  1. Run the engine at idle.
  2.  
  3. Place a finger over the end of the PCV valve to check for vacuum. If there is no vacuum, check for clogged valve.
  4.  
  5. If the engine is idling rough, this may be caused by a clogged valve or plugged hoses. Never adjust idle speed without checking the PCV valve first.
  6.  
  7. Turn the engine OFF and remove the valve. Shake the valve and listen for a rattle of the needle inside the valve. If the valve does not rattle, replace the valve.
  8.  

REMOVAL & INSTALLATION



See Figures 2 and 3



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Fig. Fig. 2: Removing the PCV valve from the intake manifold



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Fig. Fig. 3: Removing the crankcase ventilation hose from the cylinder head cover

PCV Valve
  1. Remove the PCV hose from the air cleaner assembly and from the PCV valve.
  2.  
  3. Loosen the screws holding the PCV valve retaining bracket, as required.
  4.  
  5. Remove the PCV valve from the intake manifold.
  6.  
  7. Installation is the reverse of removal.
  8.  

 
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