PCV

📖 YOUCANIC Automotive Glossary

The PCV (Positive Crankcase Ventilation) valve routes combustion blow-by gases from the crankcase back into the intake manifold for burning. The one-way metered valve restricts flow at idle (high vacuum) and opens more under load (low vacuum). Stuck closed: crankcase pressure buildup, oil leaks, sludge. Stuck open: vacuum leak, rough idle, lean codes (P0171/P0174).

PCV replacement is simple and inexpensive maintenance — recommended every 30,000-60,000 miles. Some modern engines integrate PCV into the valve cover rather than using a separate replaceable valve.