Why is my Nissan VQ25DD engine burning oil through the PCV valve after replacing it?

Question

When I plug off the pcv valve it stops smoking.

Comments

Is the excessive smoking at idle or under heavy acceleration?

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Some at idle, more on acceleration.

Answer 1

Part of the excessive smoke with the PCV valve removed is due to the engine design. One of the PCV functions is to helps regulate crankcase fumes for engine performance. No valve means no fumes regulation, and all the fumes will go directly to the combustion chamber. With the PCV valve, the fumes pressure will increase and will go through the piston seals.

Nissan VQ engines are known for developing excessive smoke and oil consumption. And, part of the problem is the design of the piston seals.

I used to work at a Nissan dealer, and we replaced many engines due to excessive oil consumption and smoke. There was not an engine failure; the problem was that the engine was not designed to run at a very high RPM.

Comments

Thanks. Wow, that's interesting. . .But then why would the smoking stop when I plug off the hose coming from the intake manifold to the pcv valve, and leave the pcv valve hole open to the atmosphere?