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Unread 03-17-2015, 11:12 AM   #1
coltd89
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1992 YJ Wrangler 
 
Join Date: Mar 2015
Location: Albertville, Alabama
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CCV not operating properly 92 4.0

For starters I do not have an airbox, the previous owner took it all out for whatever reason. I have an open pcv valve on the front with a breather filter hose clamped on and the metered pcv valve in the back with a breather filter clamped on. Where my ccv hose should run into the manifold it is plugged. My fresh air inlet on the front is blowing a lot of air out and the rear metered pcv valve or plastic elbow doesn't seem to have any pressure or suction. I have cleaned both of them thoroughly. Thoughts? Ideas? Fixes?

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Unread 03-17-2015, 01:01 PM   #2
mike134
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1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland, OH
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restore it as close to factory as you can. It'll only cost about 10 dollars. A new PCV valve is about 4 dollars and the proper vacuum hoses are a few dollars more.

Connect back to manifold so you get the extra suction and burn the fumes in the engine.

The filtered breather side can remain unconnected.

Also, get an air intake filter if you don't have one.

It should be blowing air out. It is a positive crank case ventilation. You want it sealed up and connected to the manifold to properly regulate the pressure. Do you currently have any oil leaking out of the valve cover gasket or back through the filters?
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Unread 03-17-2015, 02:09 PM   #3
coltd89
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OK I'll order the pcv and the vaccum line pronto. But to clarify, the valve nearest the front of the vehicle SHOULD be blowing out and the one closest to the firewall SHOULD have suction?
The vehicle was severely neglected prior to me getying it a couple of weeks ago. There is sludge and oil everywhere so I'm not sure what's coming from where just yet. There were 4 or 5 really loose bolts on the rear of the valve cover so it was and still may be leaking there. I did buy a new air intake filter to put on.
I replaced the oil pan gasket and rear main seal this weekend which so far has eliminated the oil leaks from underneath. I have only put about 50 miles on it since then but it doesn't appear to be using any oil YET.
I noticed light blueish smoke on idle yesterday and thicker when its revved. I concluded that regardless of what's actually causing it the ccv/pcv issue needed to be addressed
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Unread 03-17-2015, 02:41 PM   #4
mike134
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1989 YJ Wrangler 
 
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I included a couple diagrams below. I don't have the 92 manual with me, so I can't check which one is the 4.0. I think its probably the first diagram. You can tell the difference on your vehicle by the placement of the front hose port:





You should be able to get these parts at Autozone if you don't want to wait.

I would suggest replacing the rubber grommets attached to the valve cover (if your model has any) while you're working on the system. they're probably pretty brittle at this point.

The valve cover gasket is part of this system as well, If you have to remove the valve cover to remove the grommets, I would suggest a reusable Fel-pro valve cover gasket. The forum loves them. If your grommets are still rubbery enough to remove without them breaking into a thousand pieces, I'd leave the valve cover and gasket in place until it starts to leak.


I think the rear port on the 4.0 is the one that is metered. This one must connect to the intake manifold.
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Unread 03-17-2015, 04:23 PM   #5
Drednot
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Quote:
Originally Posted by mike134 View Post

It should be blowing air out. It is a positive crank case ventilation.
Hey, mike, i have to correct you on this one point. When they say Positive, they dont mean that the crankcase it presurized. They mean that there is a suction applied at one end and filtered air is drawn in at the other to force the combustible fumes out to be burned.

Other than that, you are correct that you should have a new pcv vavle at the back and the front just needs a filter to keep dusty air from entering the valve cover.

The pcv has two functions. To meter the vacuum so as not to act as a vacuum leak, and to pop shut if there is a backfire through the intake so it doesn't ignite the crankcase fumes and blow your valve cover off.

With fuel port fuel injection, that almost cant happen, so thats why they went with the ccv system. Just the orifice without the flame arresting feature.
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Unread 03-17-2015, 05:08 PM   #6
mike134
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you're right, its actually a CCV system. Even the factory service manual occasionally refers to it as a PCV system though.
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Unread 03-17-2015, 06:47 PM   #7
coltd89
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1992 YJ Wrangler 
 
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Location: Albertville, Alabama
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Thank you so much that is exactly what I needed, I went and bought some temporary hose, took off the junk that was plugged and ran a hose from the rear elbow to the manifold and maybe its just a placebo but I swear it sounds, feels and runs better. It even quit smoking. I plan to replace the valve cover gasket sometime this weekend and get proper vacuum hose. The elbows that are there appear to be in good shape with a good seal. I took the doors off and drove her about 25-30 miles this evening to get it nice and warm and it seemingly ran great. I may have a good one after all.
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Unread 03-17-2015, 07:20 PM   #8
mike134
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1989 YJ Wrangler 
 
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hah, I'm sure it is not a placebo. An engineer probably spent years figuring out the best way to vent this valve cover. It should be no surprise that some ******* previous owner couldn't hack together a better system by mistake.

Definitely go with the re-usable fel-pro valve cover gasket if you can afford the moola. Using premium parts is still cheaper than having a mechanic do it.
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