The PCV system is a whole complicated series of tube to vent the crankcase pressure. There is an oil seperator on all non-turbo cars under the intake manifold that gets clogged over years of use and will probably need to be replaced. The easy test is to warm the engine up & pull out the oil dipstick while the car is idling. If a trail of smoke puffs out of the opening, the PCV system will need to be cleaned/replaced. It's not a bad DIY job, especially on a non-turbo car, but it is time-consuming and a bit annoying.
http://www.lakesidedp.com/uploadpics/pcv/index.html
http://volvospeed.com/vs_forum/index.php/topic/101431-pcv-diy-tips-for-non-turbo-model-98-v70/
A little bit more information for you ^^^
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