8-9 years would be the suggested time frame. Keep in mind that it is not only the issue of the CCV having problems in the cold, most of these are due to soft thermostats and short drives without a longer once a week 30-45 minute highway run. But the plastic pipes become brittle, crack and break and cause vacuum leaks.
Rough idling could be a dirty idle control valve (icv, likely), a failing crankshaft position sensor (cps, unlikely) or a bad/dirty throttle position sensor (tps, also unlikely). The cps's resistance should be tested when the engine is cold and when it is hot, to see if it is in range according to its specs.

Everything I've read points toward the crankcase vent valve. Unfortunately, on this car, it is built in to the valve cover so that means I have replace the entire thing at over $400. I'm wondering if anyone knows of a fix for this other than replacing the valve cover. Any help is appreciated. 04-04-2015, 01:04 PM #2.

SYMPTOMS OF BAD PURGE VALVE. HOW TO KNOW PURGE VALVE IS BADIn this video we are going to explain the symptoms of a bad purge valve. Purge valve can fail in a First with the engine at warm idle with the vacuum hose connected to the fuel pressure regulator take a measurement. This is the low end fuel pressure. The next thing you do is disconnect the vacuum hose from the fuel pressure regulator and then take a fuel pressure measurement. This is the high end fuel pressure.
BMW capped off the CCV vacuum port. In this case, they didn't modify the diagram at all so it's wrong in that hose #6 is actually endcap #15 (not shown on the diagram or in the parts list) BMW changed the L connector to an F connector so that the hose that previously got suction from the CCV would now get suction from the F connector
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bmw e46 ccv valve symptoms