Here's a step-by-step guide on how to replace the PCV valve. The engine used in this guide is a 4.9-liter inline-6 in a 1991 Ford F-150. This engine is also referred to as the Ford 300 .

The positive crankcase ventilation valve releases exhaust gas and unburned fuel from the engine block into the intake manifold. All engines allow some exhaust gases, unburned fuel and oil to ...