Im doing a tune up on my car and i guess i should repalce the PCV valve as well. What does this part actually do?

 

A couple of stealerships have told me that the PCV valve seldom needs to be replaced. They are relatively cheap and don't fail as often as they used to.

The Positive Crankcase Ventilation (PCV) system reduces hydrocarbon emissions by scavenging crankcase vapors. It does this by circulating fresh air from the air filter through the crankcase, where it mixes with blow-by gasses and is then routed through a PCV valve to the intake manifold. The PCV system consists of a replaceable PCV valve and the crankcase ventilation hoses.

See Section 1-23 of the Haynes manual. Its located in the rear valve cover, just behind the throttle body. To check if its functioning properly, pull the PCV valve out of the rear valve cover and verify that vacuum is felt at the valve with the engine running.

They don't have to be replaced very often anymore. They cost very little. See section 1-23 of the Haynes manual. The PCV valve is located in the rear valve cover, just behind the throttle body. Pull the PCV valve out of the rear valve cover and verify that vacuum is felt at the valve with the engine running at idle. Place your finger over the end of the valve. If there's no vacuum at the valve, check for a plugged hose or valve. Replace any plugged or deteriorated hoses.

If you buy a PCV valve, compare the old valve with the new one to make sure they're the same. There are aftermarket PCV valves, you don't have to buy one from the stealership.

I haven't replaced mine yet on my 95 but its a low miler.