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Changed PCV valve, and truck runs much better...

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Old 03-11-2011, 10:12 PM
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Default Changed PCV valve, and truck runs much better...

When I bought my truck about six months ago, I went to the parts store and bought a new aftermarket pcv valve. Since then, I have been reading this site and learning that the factory piece works better.

I went down to the local dealership today and bought a new OEM pcv valve. I went out and installed it before leaving, and noticed an immediate difference in the way the truck ran.

Now I am actually ignorant on the workings of the pcv valve, and why it is so important in the way the engine runs, and why the OEM part works better.

I have done a search on here, but the search engine does not accept "pcv". I get a message that the search criteria is too short. I tried "pcv valve", but got a bunch of threads where folks recommend changing them, but no real info.

Please help me learn. Thank you in advance. Josh

By the way, the dealership charged $5.41 for it. Not too bad.
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Old 03-11-2011, 10:14 PM
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what kind of difference did you notice before and after?
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Old 03-11-2011, 10:32 PM
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Before I changed it, the truck seemed kind of doggy, like it was a real effort to accelerate.

Did you ever have days where it seems like your truck just wants to race down the road without even trying? My truck was kind of the opposite. Even going up a very slight grade it wanted to downshift all the time when I barely pushed the throttle.

Now that I have the OEM one in, it seems to have a little bit more get up and go. Acceleration is a little better. Now I can push the throttle down a little bit and it picks up speed with shifting so much.

I am hoping my mileage will improve slightly. My next project for this weekend is to install my 14x3 K&N and filter lid. After that I might consider getting rid of the cat, and putting in a piece of pipe in it's place. I was going to gut it, but a friend of mine who used to sell scrap told me I should be able to get about $100 for it at the junk yard.
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Old 03-11-2011, 10:40 PM
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a friend of mine who used to sell scrap told me I should be able to get about $100 for it at the junk yard.
I HIGHLY doubt it. You'll get right around $30 for it. That's how much I go for mine. Assuming you have only 1 cat.
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Old 03-11-2011, 11:38 PM
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Originally Posted by Josh_Putman View Post
Now I am actually ignorant on the workings of the pcv valve, and why it is so important in the way the engine runs, and why the OEM part works better.

{ ... }

Please help me learn. Thank you in advance.
Okay...

The whole purpose of the PCV system is primarily to keep the oily air in your crankcase from being dumped directly onto the highway (and into the air, but this concern came later), and secondarily (as an afterthought, really) to keep that same oily air from squeezing past your piston rings during intake strokes to be baked onto your pistons and cylinder walls. It does this by providing a place for crankcase pressure to go -- into your combustion chambers along with the intake charge.

It's far from a perfect system but it's an economical balance.

We can't just plumb a pipe from the crankcase to the intake manifold because such a system would suck way more oil into the combustion chambers than would be good for them. In no time at all the valve stems would look like fudgesicles of carbon and the tops of the pistons would be buried under a thick insulating blanket of carbon because all of that oil would bake onto anything and everything it could settle upon. Things would get hot fast, and we'd be driving along listening to pinging until our engines failed prematurely and often dramatically. The fudgesicle valve stem deposits would eventually grow high enough up on the stems to interfere with the valve guides, stretching the valve stems and wearing the guides so that in addition to the PCV system we'd now be drawing oil directly through the valve guides in a nasty vicious cycle.

So along comes the PCV system and the valve itself. Air is drawn in through one valve cover (the one that has a hose connected to your air cleaner body), passes through the crankcase, and is drawn out through the opposite valve cover, PCV valve, and into the intake manifold. Feaky snuckers that we are, modern PCV systems draw air that's been cleaned by the air filter so we don't suck dust or condensed water droplets into the crankcase.

The purpose of the valve is to modulate this air flow. With just an open pipe we'd suffer perpetually low engine vacuum which would harm both performance and fuel economy, and during our higher vacuum operation modes (idling, cruising, decelerating) we'd pull oil droplets flying off of our rocker arms in the fast moving air stream right into the intake manifold -- which would lead to those fudgesicle valves and blanketed pistons. So inside the valve there's a spring with a piston attached that regulates flow. During high vacuum the valve reduces flow, and during lower vacuum it increases flow. This keeps the volume of air flowing through the system moderated if not constant, and prevents those oil droplets from hanging in fast-moving air to be sucked into the combustion chambers. And it just happens that we get the most blow-by during low vacuum operation as when mashing the pedal to the floor, so opening up the air flow then makes good sense as it prevents crankcase pressure from building to push that oily air past the rings on the intake strokes of our pistons.

I'm into my fourth tequila after a trying week so I may very well have missed some salient point, but that's the PCV system in a nutshell.

The trick with aftermarket valves is that some are too generous and some are too stingy -- you get either too much air flow and so suck oil off of the valvetrain, or you get not enough flow and push some oil past the rings. Both will show increased oil consumption and be very ungood for your truck. The oil is cheap enough, but the things it fouls when it's burnt are spendy. Things like cylinder walls, pistons, oxygen sensors, and catalytic converters, not to mention fuel economy in these $4/gallon days.

So now ya know.
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Old 03-12-2011, 12:04 AM
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nice post. never knew that's what the hose to the air cleaner was for, and that it eventually routed to the pcv valve. But i'm a noob. Good info tho
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Old 03-12-2011, 05:11 AM
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Thanks a ton, UnregisteredUser. Now I get the picture.

I'm just glad I did it, as I have a half hour commute to work one way, and I filled my truck on Monday, and had to add another $20 yesterday so I wouldn't have to walk. I have to add another $20 today for the same reason.

Man, this thing sucks the gas!
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Old 03-12-2011, 05:11 AM
 
 
 
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