Pressure control valves are typically installed on the top of the engine, on the valve cover.

PCV stands for Positve Crankcase Ventilation. You will find the valve located on the valve cover, with a hose running to it. If you know where the brather filter is (look under your air filter) you can follow the hose that runs out of the breather filter to the PCV valve. Make sure to check the rubber grommet that the PCV valve sits in for signs of deterioration. It's only a few bucks and is easy to replace, so if it looks bad replace it. If the PCV valve was bad, chances are the breather filter is due for replacement as well. That should also run only a few dollars, so if it's dirty get a new one.

The breather filter hose will NOT lead you to the PCV valve. The breather filter is separate from the PCV valve. The PCV valve connects to a hose that goes to your intake manifold. I don't have your vehicle, so I can't tell you where the oil separator is. However, I own a 1951 Chevrolet with an oil separator. The system is passive. There are louvers in the valve cover (stupid idea that lets road dirt into the oil), and there's a draft tube that comes out of the crankcase, which forms a vacuum while you drive (aire goes into the valve cover louvers, and out of the draft tube). The tube first goes up in a canister formation, and then a downward stack slants slightly towards the rear. In the canister part is the separator. It's a two part canister that allows the fumes to get out, but has an inner canister for oil to condense on and flow back into the engine. Many engines with a PCV valve have the valve on the cover. The ideal place to take the gasses, though, is from the crankcase, since that's where they originate. If you take the gasses directly from the crankcase, and not from on top of the engine, you must have a device that separates the oil spray and splash from the vapors, or else oil will be carried into your intake manifold in unacceptable amounts. The oil separator on your engine may take the shape of a small canister, most likely mounted to the crankcase, but will not have a draft tube, since your engine doesn't use passive ventillation, but rather a PCV valve. The breather, on the other hand, lets air into the engine crankcase (usually not at the crankcase, but instead at the valve cover) under normal circumstances, to replace air that is drawn out by the PCV valve (remember that the PCV valve also draws out blow-by gasses). When the throttle is opened wide, air would rather go through the throttle passage than through the PCV valve, so the PCV valve doesn't do too much at wide open throttle. However, the breather is on the air cleaner, and will be exposed to the high draw of the open throttle. The breather will start to draw gasses out, too. Together they will evacuate the crankcase, which is especially needed at wide open throttle, since that is when the most blow-by is created. (I explained this because another person wrote that the PCV valve is connected to the breather hose.....I want to show the clear difference between the PCV valve and the breather. Both are needed in the crankcase ventillation system, but they are not the same thing, and are not connected to the same hose.) Although I didn't tell you exactly where your oil separator is, I hope that this proper explanation of the PCV system will give you an idea as to what you're looking for, and how to go about finding it (again, the oil separator is most likely a canister of sorts mounted down on the crankcase--the area where the crankshaft is located). The PCV valve is at the end of a vacuum hose that goes to your intake manifold after the throttle (in a few engines, it'll be slightly before the throttle, so that it isn't exposed to vacuum until the throttle opens). Also, PCV valves rarely fail. They're oil soaked all the time from the fine spray of oil that does get to them, so they don't usually corrode. What can happen is that they can become clogged, or the spring can break. Soak in acetone if there's no plastic, or carburetor cleaner if there is plastic. If the plunger doesn't push almost shut with the valve upside down, the spring may be broken. Also, push the plunger in with a pencil to check travel. You can also check operation on the engine by kinking the PCV valve hose. Plunger should pull in to reduce airflow to a minimum amount when vacuum is applied, and plunger should push all the way out to the backfire protection position when vacuum is removed (intermediate positions allow for a lot of air flow, and only occur when the engine is under load, and vacuum levels are reduced, but not eliminated). If there are excessive gasses and foam in the crankcase, the valve spring may be broken or the unit may be clogged (as well as associated hoses). Clean well. If the engine won't idle properly, the unit may be clogged or it may be faulty and worn (rarely...people say that they break all the time, which they don't....they're usually just dirty), or you could have a leaky hose. Clean the valve well, replace leaky hoses, and replace the breather filter. Replace the valve if you still can't correct trouble (If you still can't get a good idle, and your engine still is lean, you may have trouble elsewhere....also, if your engine idles improperly, and is running rich, this may be due to too much fuel in the oil, possibly due to flooding of the engine at some point, and cannot be cured unless the engine is either taken for a long drive, or the oil is changed....excessive vapors in the oil will richen the intake manifold mixture, though modern engines usually compensate for this with the computer...it's more of a problem in a carbureted car). After market valves often don't perform as well as factory originals. Don't replace unless you need to. PCV valves, as I've said before, can last for decades. It's also important that all seals are in good condition, because leaks can reduce the efficiency of the system, and also introduce excessive air that might lean out your engine. Also, if you're curious about the PCV valve's backfire protection position, it's there to prevent backfire from entering the crankcase. If backfire reached the blowby gasses in the crankcase, the crankcase would explode. Thomas