I have a 1995 Firebird with almost 30,000 miles. I was in the dealership where I had bought the car for an oil change, and the mechanic said that I should also replace the PCV valve. He said that Pontiac recommends replacing it about every 6,000 miles. This seems really early to be replacing parts on an almost new car. Is this the right time to change it, and what does the PCV valve do?
Let's define a PCV valve. PCV stands for Positive Crankcase Ventilation. The valve itself controls the amount of intake manifold vacuum being directed to the interior of the engine's crankcase.
When the combustion process takes place there is always a certain amount of harmful vapor which gets past the piston rings after the explosion, this is called "Blow-By". So the PCV valve applies vacuum, and literally sucks the bad gases and excessive pressure out of the crankcase and back into the engine's intake manifold. Once there, the engine burns it up, preventing mechanical damage to the engine and emissions-related damage to the atmosphere.
I pulled up the factory recommended services for '93 to '95 Firebirds and Camaros. They suggest inspecting and servicing (cleaning) the PCV valve every 30,000 miles, and nowhere do they advise replacement. Dealerships will often use their own service schedules which don't exactly coincide with the manufacturer's schedule. This is probably the situation that you've run into.
My suggestion would be to go ahead and replace the valve at 30K. By this time there will be the start of a carbon build-up inside the valve that may affect its operation. I don't care what anybody says, but it's crazy to attempt cleaning such an important yet inexpensive part.
On certain applications there is a PCV filter or breather element on the side of the engine opposite the valve itself. This is to keep the outside air entering the engine as clean as possible, and should be replaced along with the valve. Note: Don't use anything but an AC Delco PCV valve or you're asking for trouble.