Repair Pontiac Mid-size 1974-1983 Repair Guide

Positive Crankcase Ventilation (PCV) Valve

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Fig. Fig. 1



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Fig. Fig. 2 Typical Positive Crankcase Ventilation (PCV) system flow



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Fig. Fig. 3 Checking the PCV valve for vacuum at idle

All gasoline engines covered in this guide are equipped with a closed crankcase emission control system (see ) featuring a vacuum-operated Positive Crankcase Ventilation (PCV) valve. A faulty PCV valve or clogged hoses to and from the valve can cause a rough idle, oil leaks, or excessive oil sludging. Check the system at least once a year and replace the valve at least every 30 months or 30,000 miles. A general test is to remove the PCV valve from the valve cover and shake it. If a rattle is heard, the valve is usually OK.

A more positive test is:

  1. Remove the PCV valve from the rocker arm cover or intake manifold.
  2.  
  3. Connect a tachometer to the engine and run the engine at idle.
  4.  
  5. Check the tachometer reading, then place your thumb over the end of the valve. You should feel a suction.
  6.  
  7. Check the tachometer again. The engine speed should have dropped at least 50 rpm. It should return to a normal idle when you remove your thumb from the end of the valve.
  8.  
  9. If the engine does not change speed or if the change is less than 50 rpm, the hose is clogged or the valve defective. Check the hose first-if it is not clogged, replace the PCV valve. Test the new valve in the same way.
  10.  

REMOVAL & INSTALLATION



The PCV valve is located in the rubber grommet in the valve cover, connected to the air cleaner housing by a rubber hose. To replace the valve:

  1. Pull the valve (with the hose attached) or the hose from the rubber grommet in the valve cover.
  2.  
  3. Remove the PCV valve from the hose.
  4.  

To install:

  1. Install a new PCV valve into the hose.
  2.  
  3. Press the valve or hose back into the rubber grommet in the valve cover.
  4.  

 
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