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 .

My emissions control diagram for the 2000 model year (I split the difference) E-150 shows the PCV (positive crankcase ventilation) valve on the top, rearward end, of the right-bank valve cover.