GM Storm/Spectrum 1985-1993 Repair Guide

Positive Crankcase Ventilation System

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OPERATION



See Figures 1 and 2

The system consists of a tube from the air filter housing to the rocker/camshaft cover and a second tube from the rocker/camshaft cover to the intake manifold. Under normal operating conditions, clean air flows from the air filter into the rocker/camshaft cover where it mixes with crankcase oil vapors. These vapors are drawn through the PCV valve and into the intake manifold to be burned with the air/fuel mixture. The flow to the intake manifold is metered by the PCV valve (either a regulating orifice or vacuum diaphragm type). When manifold vacuum is high, the valve restricts flow to maintain a smooth idle. If crankcase pressure is very high, vapors can flow directly into the air filter housing.

A plugged PCV system may cause a rough idle, stalling, oil leaks and/or a build up of sludge in the engine. An air filter coated with engine oil, indicates excessive crankcase pressure. A leaking valve or hose might cause; a rough or high idle and/or engine stalling.



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Fig. Fig. 1: PCV valve system schematic - Spectrum



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Fig. Fig. 2: PCV valve system schematic - Storm

SERVICE



  1. Visually inspect the PCV valve hose and the fresh air supply hose and their attaching nipples or grommets for splits, cuts, damage, clogging, or restrictions. Repair or replace, as necessary.
  2.  
  3. If the hoses pass inspection, start the engine and allow it to warm until normal operating temperature is reached.
  4.  
  5. Remove the PCV valve from the rocker arm cover, but leave it connected to the hose. With the engine at idle, feel the end of the valve for manifold vacuum. If there is no vacuum, check for a plugged or leaking hose, PCV valve or manifold port. Replace a plugged or damaged hose.
  6.  
  7. Stop the engine and remove the PCV valve. Inspect the orifice for plugs or restriction. If restricted, clean the orifice to allow proper flow.
  8.  

REMOVAL & INSTALLATION



See Figures 3 and 4

  1. For carbureted vehicles, it may be necessary to the remove the air cleaner assembly for access to the PCV valve.
  2.  
  3. Remove the PCV valve from the mounting grommet in the rocker/camshaft cover.
  4.  
  5. Disconnect the valve from the PCV hose and remove the valve from the vehicle.
  6.  
  7. Installation is the reverse of the removal procedure.
  8.  



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Fig. Fig. 3: PCV valve installation - Storm SOHC engine



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Fig. Fig. 4: PCV valve installation - Storm DOHC engine

 
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