The PCV valve on Altimas looks different than what has been common for
years on most engines. The PCV valve
is located at the drive belt side
of the engine under the intake manifold and attached to the
breather/separator. Access from above is very difficult; access the
valve from underneath the vehicle. There is a short hose that connects
to the breather/separator.
Remove the breather/separator and the hose.
Then you can unscrew the PCV valve from the breather/separator for easy
inspection and cleaning of each piece. Also inspect both passages where
the separator and hose connect. Here is a picture of the valve after it
is removed. The breather/separator is a small aluminum housing that will
fit in your hand.
Obviously the PCV system is more difficult to service on Altima engines
than the more familiar design on so many other engines. A restriction in
the PCV system will increase crankcase pressure. This pressure inside
your engine will push oil out where ever it can find a place to leak,
including into the distributor.