Another grinding question....Nissan Pickup
Smoke shouldn't be coming from the oilcap, that hole should have vacuum to it when you place your hand over the hole.
Check for a line from a valve cover to the intake manifold, they usually have a small orifice that becomes clogged or the entire line becomes clogged with soot. Clean this and the pressure built up in the crankcase by normal blowby will be vented into the intake.
If you have a jeep, Check the line at the front of the valve cover, there should be a brass fitting were it attached to the valve cover. This fitting may have a small orifice that's clogged. If not, look midline in this hose for a plastic coupler, it has the small easily clogged orifice. I think I could say orifice a few more times, don't ya think?