A properly working PCV system vents pressurized air inside the crankcase due to blow-by, back into the intake system downstream of the airflow sensor. The highest flow is under low vacuum (high load). The "fresh air" supply which feeds the crankcase is usually routed from the air cleaner itself or from the intake tube upstream of the airflow sensor.

The pressurized air inside the crankcase would smell like burned oil or combustion gasses.

A sticking PCV valve would either be too open or too closed at idle or under load, which would cause driveability/idle problems.

If the valve is stuck closed, you'll get oil stains at the filtered air feed tube due to the positively pressurized air in the crank case, which is laden with oil, soot, acidic compounds, etc... but wouldn't necessarily cause poor idle - unless it coats your IAT sensor to the point that it can't take proper readings, or clogs the idle air bypass in the throttle.

If the valve is stuck open, you'll get excess un-metered air pulled into the intake downstream of the airflow sensor, which will cause idle problems - but you won't get any oil at the fresh air feed.

My guess is that it's sticking; it would explain all of your problems.

You should be able to check the PCV valve by shaking it. If it doesn't rattle, it's no good. If you can blow through it both ways, it's no good.

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A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608

Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL.