Positive Crankcase Ventilation: Testing and Inspection

Checking PCV Vacuum:

*** UPDATED BY TSB# 90C29, DEC. 1990

PCV SYSTEM

A. Remove PCV hose from PCV valve

B. Run engine at idle

C. Place your finger over the end of the PCV valve to check for vacuum. If there is no vacuum, check for clogged valve. Replace as necessary.

D. Reconnect PCV hose to PCV valve.

E. Check PCV hoses for connection, leakage, clog and deterioration. Replace as necessary.

NOTE: If engine is idling rough, this may be caused by a clogged PCV valve or plugged hoses; therefore, never adjust idle speed without first checking PCV valve and hoses.

GENERAL MOTORS has determined that ALL 1989-90 Geo Trackers have been built with a positive crankcase ventilation (PCV) breather hose which may freeze during extended driving at low ambient temperatures due to its narrowness (below -4 Fahrenheit, -20 Celsius). Freezing of this passage results in loss of engine oil and engine damage. To correct this condition, A larger PCV breather hose will be installed.

WARNING: An engine which is operated without any crankcase ventilation can be damaged. Therefore, it is important to replace the PCV valve at intervals shown in MAINTENANCE PROCEDURES. Periodically inspect the hoses and clamps and replace any showing signs of deterioration.