A bad or the wrong PVC valve can cause oil use, and other engine related issues. I learned that the hard way. I did a major tune up many years back on a Ford van I owned and PCV replacement was part of the Tune Up. Being cheap and lazy I use a Fram PCV valve and my van started using oil, and didn't idle as well. It never used a drop until then. After driving myself nuts checking for leaks, engine timing, vacuum leaks etc, the only thing I could think of was to change the PCV valve back to a Motorcraft PCV valve. Oil use stopped, idle went back to the way it always was. Since that day I will only use an OEM PCV valve!