What effect does a stuck open PCV valve have on engine operation?

When the Positive Crankcase Ventilation (PCV) valve becomes stuck open, it creates an uncontrolled air leak into the intake manifold. This situation results in a vacuum leak, which alters the air-fuel mixture entering the engine. The engine control module (ECM) may not be able to compensate for this extra air, leading to a lean condition—where there is too much air in the mixture compared to fuel. This can cause rough idling, poor acceleration, and overall decreased engine performance, as well as potential misfires due to the improper air-fuel ratio.

Additionally, a stuck open PCV valve can negatively impact other systems in the vehicle, such as emissions control. It can cause increased hydrocarbon emissions since unburned fuel can escape from the combustion process. Understanding the role of the PCV valve is vital, as it regulates the flow of blow-by gases from the crankcase to the intake manifold, thereby helping to maintain proper engine operation and efficiency.