Positive Crankcase Ventilation: Testing and Inspection

PCV Valve (Typical):

PCV Flow (Typical):

Results of Incorrect Operation

A plugged valve or hose may cause:
- Rough idle.
- Stalling or slow idle speed.
- Oil leakage.
- Oil in air cleaner.
- Sludge in engine.

A leaking PCV valve or hose may cause:
- Rough idle.
- Stalling.
- High idle speeds.

Pre-Checks
With these systems, any blow-by in excess of the system capacity (from a badly worn engine, sustained heavy load, etc.) is exhausted into the air cleaner and is drawn into the engine. If oil sludging or dilution is noted and the PCV system is functioning properly, check the engine for possible cause and correct to ensure that the system will function as intended.
Proper operation of the PCV system is dependent upon a sealed engine. Check for a correct PCV valve and a properly mounted valve into the rubber grommet. Make sure the hose(s) and clamp(s) are tight, and in place.

Functional Checks
1. Start the engine, and let idle.
2. Remove PCV valve from valve cover, and 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.
- Check manifold port.
- Check PCV valve.
3. Remove engine oil dipstick and install a vacuum gauge on dipstick tube.
4. Run the engine at 1500 rpm for 30 seconds, and then take a vacuum gauge reading at that same engine speed. If vacuum is present, then system is OK. If no vacuum is present, the engine may not be sealed and/or drawing in outside air. If pressure registers on the gauge, check for a plugged hose or excessive engine blow-by.
5. Turn the engine "OFF," and remove the PCV valve from hose. Shake the valve and listen for the rattle of the check needle inside of the valve. If it does NOT rattle, replace the valve.