Positive Crankcase Ventilation: Testing and Inspection

***UPDATED BY TSB #EM91004, APRIL 1991
^This engine incorporates two PCV valves, one on the outside/bottom of each intake plenum.
1. Start engine and idle.

PCV Test:

2. Remove hose from PCV valve and check for vacuum.
If strong vacuum exists proceed to step #4
If not proceed to step #3.
3. Remove PCV valve and shake to check if it is sticking.
If OK proceed to step #4.
If not OK, replace valve.

PCV Hose Test:

4. Check all hoses for restrictions.
Clean or replace hoses as necessary.
Repeat the procedure for the other valve and hose.

Fig. 47 PCV Valves:

On some 1990 300ZX vehicles, the engine emit a spark knock (detonation) noise when accelerating under no load. It has been determined that the PCV valve(s) may be the cause.
While duplicating the noise either remove or pinch off the hose to the PCV valve, if the noise goes away you will need to replace both PCV valves and hoses. If the noise is still present refer to "Diagnosis By Symptom" in "Testing Procedures".


PART NAME NEW PART # OLD PART #
Valve Assembly-Control 11810-40P00 11810-30P00
Hose-Blow By 11823-30P01 11826-30P01
Hose-Blow By 11823-30P11 11826-30P11
^2 of each part required.