GM Cavalier/Sunfire 1995-2000 Repair Guide

PCV Valve


All of the vehicles covered by this guide with the 2.2L engine utilize a Positive Crankcase Ventilation (PCV) or Crankcase Ventilation (CV) valve, which regulates crankcase ventilation during various engine running conditions. At high vacuum (idle speed and partial load range) it will open slightly and at low vacuum (full throttle) it will open fully. This causes vapors to be drawn from the crankcase by engine vacuum and then sucked into the combustion chamber where they are dissipated.

The PCV system must be operating properly in order to allow evaporation of fuel vapors and water from the crankcase. This system should be serviced and the PCV valve replaced every 30,000 milee (48,000 km). Normal service entails cleaning the passages of the system hoses with solvent, inspecting them for cracks and breaks, then replacing them as necessary. The PCV valve contains a check valve and, when working properly, this valve will make a rattling sound when the outside case is tapped. If it fails to rattle, then it is probably stuck in a closed position and needs to be replaced.

The PCV system is designed to prevent the emission of gases from the crankcase into the atmosphere. It does this by connecting a outlet (the valve cover)to the intake with a hose. The crankcase gases travel through the hose to the intake where they are returned to the combustion chamber to be burned. If maintained properly, this system reduces condensation in the crankcase and the resultant formation of harmful acids and oil dilution. A clogged PCV valve will often cause a slow or rough idle due to a richer fuel mixture. A vehicle equipped with a PCV system has air going through a hose to the intake manifold from an outlet at the valve cover. If the PCV valve or hose is clogged, this air doesn't go to the intake manifold and the fuel mixture is too rich. A rough, slow idle results. Clamp the hose shut. If the engine speed decreases less than 50 rpm, the valve is clogged and should be replaced. If the engine speed decreases much more than 50 rpm, then the valve good. The PCV valve is an inexpensive item and it is suggested that it be replaced, if suspect. If the new valve doesn't noticeably improve engine idle, the problem might be a restriction in the PCV hose.

For the 2.3L and 2.4L engines, blow-by gases are passed through a Crankcase Ventilation (CV) oil/air separator hose into the intake manifold. Incorporated in the CV system is a crankcase ventilation heater assembly, a positive temperature coefficient device, which serves to prevent icing in the CV system.

More information regarding the PCV/CV system, including system tests, is located in Emission Controls of this guide.



See Figures 1, 2, 3, 4 and 5

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Fig. Fig. 1: The PCV valve is attached to the intake by a hose and is located in the valve cover and held by a plastic retainer

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Fig. Fig. 2: Use a pair of pliers to loosen the PCV valve retainer

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Fig. Fig. 3: Unthread the retainer from the valve cover to expose the PCV valve

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Fig. Fig. 4: Pull the PCV valve from the valve cover grommet and ...

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Fig. Fig. 5: ... remove the valve from the hose

The valve is located in a rubber grommet in the valve cover. The valve has a plastic threaded retainer securing it. The valve is connected to the air cleaner housing by a large diameter 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.
  3. Remove the valve from the hose.
  5. Install a new valve into the hose.
  7. Press the valve or hose back into the rubber grommet in the valve cover.
  9. Install the retainer and tighten it with a pair of pliers.