whats a pcv valve?

[Stealth]

what are they, where do they go, and why does it say change every 1 year ? its the 3.1 mpfi btw

[mihela816]

Its a little valve on the rear valve cover, hard to see, harder to get at. It puts a vacuum on the crankcase for emissions control.

[DaveFromColorado]

it's more then emissions control.

 

it's the Positive Crankcase Ventilation valve and it's used to suck the blowby gasses out of the combustion chamber and burn them thru the exhaust. this will help your oil last longer, your rings seat better, and your engine stay cleaner. The only reason the emissions people are worried about the PCV system is because without it you'll get more blowby, and your engine will burn up faster causing greater NOx emissions.

 

--Dave.

[Stealth]

okay how hard is it to change?

[pitzel]

Once a year replacement of the PCV is very excessive as well if you actually give the engine an oil change or two per year. I would suggest, if you keep your vehicle otherwise appropriately maintained engine-wise, that you could inspect/replace (as necessary) the PCV at the same intervals as you would replace the spark plugs. As the PCV on the 3.1 is on the back of the engine, when you have the engine tilted for spark plug replacement is an excellent opportunity to remove and inspect the PCV. Otherwise it is a huge pain to inspect/replace.

 

The reason PCV systems exist is that blowby gasses will cause pressure buildup in the crankcase with blowby gases as well as the decomposition products/boiloff products of motor oil. Instead of dumping these byproducts directly into the atmosphere, the PCV system allows them to be sucked back into the engine to be reburned. Has little to do really with NOx emmissions, and everything to do with HC emmissions.

[pitzel]

okay how hard is it to change?

 

I did mine without the engine tilt trick as required for the spark plugs on a 1992 4-door Cutlass Supreme. Had to remove the MAP sensor though. I would highly recommend that you use the procedure for tilting the engine as is used for spark plug changes (and inspect the plugs at the same time).

 

If you are experiencing any sort of clogging problems on the PCV, use a different brand of motor oil. I would suggest a heavy-duty diesel oil such as Esso XD-3 0W30, which has an extremely strong anti-carbonization additive package and its vapours should be able to dissolve some of the deposits. XD-3 0W30 is also cheap, less than $15 for a 4L jug at Esso distributors in Canada.

[GutlessSupreme]

As the PCV on the 3.1 is on the back of the engine, when you have the engine tilted for spark plug replacement is an excellent opportunity to remove and inspect the PCV. Otherwise it is a huge pain to inspect/replace

 

I couldn't even get it out with the engine tilted.. not enough room to be able to play with it and get it out of the hose.

 

The easiest way is probably to just take the plenum off and change it. It's more work, but a lot less frustration. I changed mine and went ahead and degreased/painted my plenum while it was off.

[pitzel]

Nasty Gutless. Let me assure you, even when I did change it, it was a very nasty job, took me a good afternoon, half a case of beer, and all that to pull replace factory-installed PCV valve that was spotless and in perfect working order after 65k miles.

 

Car had Pennzoil 10W30 in it, changed every 1000 miles though when Grandpa owned it. Grandpa was a bit obsessive-compulsive when it came to his oil changes, but it sure has paid off in terms of PCV cleanliness.

[Stealth]

well I change the only every like 4-6000 kms so your saying that if the oil isnt left to get tehat dirty then the pcv valve will still be good for along time?

[pitzel]

Yes. Gunk in the PCV is directly related to the cleanliness/quality of the oil you use. Its a symbiotic relationship; bad PCV will make the oil go bad quicker. Bad oil will gunk the PCV up quicker.

 

Best overall life will come by selecting an oil that has low NOACK volatility, high flashpoint, and has a strong detergency package. 4-6000km's, unless your driving is all city, and is done like a maniac, probably even is excessive with a decent dino or synthetic oil.

[Stealth]

I use regular quaker state 5w-30 peak performance

[pitzel]

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=1;t=004911

 

The Quake State Peak Performance seems to be middle-of-the-road on those tests, and the oils they tested all seem to be fairly good oils, some being top-of-the-line $8/L synthetics.

 

These engines really are said to be among the easiest engines on oil, so unless you see sludge on the dipstick or underneath the drain cap, I wouldn't be too worried about the PCV unless the car has a ridiculous number of miles on it.

[DaveFromColorado]

...

 

NOx emissions are formed when enough heat and pressure exist in a vehicle's combustion chamber to combine oxygen with nitrogen. In the 1970s, vehicle manufacturers attempted to control NOx emissions by preventing their formation. They lowered compression ratios, retarded ignition and cam timing, and installed exhaust gas re-circulation components to lower combustion temperature

 

a poorly maintained engine with poor oil quality and poor crankcase venting will increase the heat in the chamber this raising the NOx emissions, where as HC emissions are typically caused by late ignition, bad catalytic converter, bad pressure regulator (too high pressure) or cam timing problems.

 

do you want me to keep going?

 

--Dave.