ASE Doc

I'm afraid you misunderstand what I meant. The PCV system is designed to provide positive evacuation of the crankcase. At idle, with intake pressure low(vacuum), air is drawn through the crankcase from the orifice connecting to the intake manifold. At the other end of the system is the make up air tube where filtered air is drawn in from the intake air tube. Under load, such as when accelerating, intake pressure rises toward atmospheric pressure. Evacuation through the orifice slows or stops and any pressure is vented into the intake air tube through the make up air tube. While the small orifice may become clogged, the make up air tract is much larger diameter and I have never seen it clog. As long as the make up air tube is open, pressure will not build inside the crankcase. Still, without normal function of the PCV system with an open orifice to the intake manifold, the PCV system can't do its job of proactively evacuating condensation and combustion gases from the crankcase. Once again, a vented cap isn't going to help this. Only clearing out the clogged orifice will restore normal function. What a vented cap will do is provide a path for unmetered, unfiltered air into the crankcase.

You can test for a clogged PCV orifice by letting the engine idle and looking for a slight vacuum at the make up air tube. Assuming the rings are working, you should get vacuum in the crankcase with the make up air tube closed briefly. If no vacuum, the orifice is probably blocked.

Darone

I'm sorry, but maybe you are unfamiliar with how the vented cap(fc219) works.
it is a pressure release cap and is designed to release pressure from the crankcase, but only if the negative pressure in the crankcase goes to positive. The release point is 1.5 to 2.0 pounds. The system remains sealed and under vacuum unless the pcv is blocked. At which point the gasses trapped in the block can escape through the valve in the cap. Makes sense to me. I can only assume that you are thinking vented cap as in 1950's design. I agree that something along those lines would have a negative effect on the engines operation. This is a GM fix used on the 2010-2013 2.4 motors. I am only guessing that telling people to do this on more current models, would be an admission that they have done nothing to fix original problem. And given they have been sued already over this issue, they don't want to admit to anything..