Disconnect CCV valve hose and check for vacuum. If you have vacuum on the CCV I got bad news. When combustion blows out the oil cap when there should be a slight vacuum if the rings are sealing good. Excessive blow-by is because the piston rings are not sealing against the cylinder walls and combustion gases are filling the crankcase.
You can check this with a leak-down tester or do a compression test and then add a small amount of oil through the spark plug hole. If the compression jumps up with oil on the ring top side then you know the rings are letting the combustion gas past them. I prefer a leak down at 100psi and anything more then 5% is a high mileage engine. 10%+ leak down is a damaged cylinder. When you do the leak-down if a valve is leaking you will hear it, if it's a cylinder ring issue the blow-by will come out the oil cap |