See Figures 1, 2, 3, 4, 5 and 6
All gasoline engines covered in this guide are equipped with a closed crankcase emission control system (see Emission Controls ) featuring a vacuum-operated Positive Crankcase Ventilation valve (PCV). 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:
- Remove the PCV valve from the rocker arm cover or intake manifold.
- Connect a tachometer to the engine and run the engine at idle.
- Check the tachometer reading, then place your thumb over the end of the valve. You should feel a suction.
- 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.
- 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.