Pontiac Fiero 1984-1988 Repair Guide

Crankcase Ventilation

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OPERATION





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Fig. Fig. 1 Positive Crankcase Ventilation (PCV) system schematic-2.5L engines



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Fig. Fig. 2 Positive Crankcase Ventilation (PCV) system schematic-2.8L engines

A Positive Crankcase Ventilation system (PCV) is used to provide more complete burning of the crankcase vapors. Fresh air from the air cleaner or intake duct (V6), is supplied to the crankcase, mixed with blow-by gases and then passed through a Positive Crankcase Ventilation valve (PCV) into the intake manifold (four cyl.) or the Air Plenum (V6). The system is used on all models but not controlled by the Electronic Control Module (ECM).

The primary control is through the PCV valve which meters the flow at a rate depending on manifold vacuum. To maintain engine idle quality, the PCV valve restricts the flow when intake manifold vacuum is high.

INSPECTION & SERVICE





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Fig. Fig. 3 The PCV valve is located on the top of the valve cover-1984-86 2.5L engines



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Fig. Fig. 4 Exploded view of the PCV system used on the 2.8L engine



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Fig. Fig. 5 PCV valve location-1987-88 2.5L engines



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Fig. Fig. 6 Check the PCV valve for vacuum at idle



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Fig. Fig. 7 Remove the PCV valve and check that it is not plugged with sludge

A clogged PCV valve or plugged hose could cause rough idling, stalling, oil leaks or sludge in the engine. A leaking valve or hose may cause rough idle, stalling or high idle speed. If the engine is operated without the the PCV valve installed properly, engine damage may result. Check the valve and hose as follows every 30,000 miles:

  1. Remove the valve from the rocker arm cover.
  2.  
  3. Apply the emergency brake and place the auto transaxle in park, manual transaxle in neutral. Start the engine and run at idle.
  4.  
  5. Place your thumb over the end of the valve to check for vacuum. If there is no vacuum at the valve, check for plugged hoses at manifold port or PCV valve. Replace plugged or deteriorated hoses.
  6.  
  7. Turn off the engine and remove the PCV valve. Shake the valve and listen for the rattle of the check needle inside the valve. If the valve does not rattle, replace the valve.
  8.  

 
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