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Author Topic: Air intake / PCV valve question  (Read 1921 times)

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Offline bootguy

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Air intake / PCV valve question
« on: February 07, 2010, 08:18:29 PM »
94YJ 2.5L with automatic transmission.  Pulled the air cleaner box and Hose to the throttle body, the Hose was caked with oil and crud.  Cleaned it out, then pulled the tube from the PCV valve to the hose it was pretty filthy, so I cleaned it also along with the throttle body.  Purchased new PCV valve Rubber Grommet and new air filter, but was told that valves and rings are bad because there is oil in these places.  Now the question is fact or fiction?  Any thoughts?
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1994 Jeep Wrangler, 2.5L, automatic, 2.5" lift, 4:88 gearing, 33" tires, 2.5" exhaust from manifold back, air restrictor removed.

Offline Jeffy

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Re: Air intake / PCV valve question
« Reply #1 on: February 07, 2010, 08:48:56 PM »
Do you mean the CCV?  That's the small brass fitting on the valve cover above #1 cylinder that has a hose leading to the intake below the TB.  Your '94 does not have a conventional PCV.
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Offline bootguy

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Re: Air intake / PCV valve question
« Reply #2 on: February 07, 2010, 09:02:47 PM »
This is a PCV valve on the back of the valve cover that goes to the rubber tube between the air cleaner box the throttle body.  There is also another tube that goes from the rubber tube to a cannister on the firewall under the master cylinder.
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1994 Jeep Wrangler, 2.5L, automatic, 2.5" lift, 4:88 gearing, 33" tires, 2.5" exhaust from manifold back, air restrictor removed.

Offline Jeffy

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Re: Air intake / PCV valve question
« Reply #3 on: February 07, 2010, 09:20:41 PM »
That's a Fresh Air Vent.

Are you getting oil in your air box?
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Offline bootguy

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Re: Air intake / PCV valve question
« Reply #4 on: February 07, 2010, 09:27:47 PM »
Not in the air box itself, but in the rubber hose going to the throttle body.  It is ridged but was smooth inside from gunk filling the ridges. The air cleaner was really crappy, thought that maybe that was pulling oil mist from the engine. (path of least resistance)
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1994 Jeep Wrangler, 2.5L, automatic, 2.5" lift, 4:88 gearing, 33" tires, 2.5" exhaust from manifold back, air restrictor removed.

Offline sharpxmen

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Re: Air intake / PCV valve question
« Reply #5 on: February 07, 2010, 10:38:57 PM »
Quote from: bootguy on February 07, 2010, 09:27:47 PM
Not in the air box itself, but in the rubber hose going to the throttle body.  It is ridged but was smooth inside from gunk filling the ridges. The air cleaner was really crappy, thought that maybe that was pulling oil mist from the engine. (path of least resistance)

you're not "pulling" from the engine, there is no breather so there's no pressure differential other than the blow-by. the only place you are pulling from the valve cover is at idle when your crank gases are going thru the brass fitting above cyl 1 (the one Jeffy mentioned) and going straight into the intake but below the t/b. check the brass fitting and the fitting in the manifold, if those get clogged you get more oil in the airbox and t/b - that's what usually is the case with the Jeeps - in more extreme cases you need to take the valve cover off and give it a thorough cleaning as the gunk can block the output thru that fitting.
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Offline Bounty Hunter

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Re: Air intake / PCV valve question
« Reply #6 on: February 07, 2010, 11:34:52 PM »
There is also a small inline orifice in the tube from the valve cover to the intake below the throttle body.  This orifice commonly gets clogged with carbon buildup and causes the crankcase to push oil and crankcase vapors to other places.
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Offline dwtaylorpdx

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Re: Air intake / PCV valve question
« Reply #7 on: February 08, 2010, 12:58:08 AM »
Depends on teh year of the 2.5 some are a brass fitting at teh valve cover, some are an line orifice.

But a clogged air cleaner will suck oil the wrong way up the large breather tube and coat the air filter.

Dave
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Offline sharpxmen

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Re: Air intake / PCV valve question
« Reply #8 on: February 08, 2010, 07:54:15 AM »
Quote from: Bounty Hunter on February 07, 2010, 11:34:52 PM
There is also a small inline orifice in the tube from the valve cover to the intake below the throttle body.  This orifice commonly gets clogged with carbon buildup and causes the crankcase to push oil and crankcase vapors to other places.

he's got a '94 so i think his is in the valve cover (the brass fitting).

Quote from: dwtaylorpdx on February 08, 2010, 12:58:08 AM
Depends on teh year of the 2.5 some are a brass fitting at teh valve cover, some are an line orifice.

But a clogged air cleaner will suck oil the wrong way up the large breather tube and coat the air filter.

Dave

there's no breather, everything is behind the air filter so there's no "sucking" thru the crank/valve cover air flow path - not sure if i explained it well enough, i didn't finish my coffee yet so i might not make much sense, but what i'm trying to say is that in case your air filter is clogged and you have a breather in the valve cover then there will be a slight pressure drop behind the air filter which would result in some air going thru the breather and then thru the valve cover to the airbox - not the case with the Jeep, all the hoses are behind the air filter so they would see the same pressure drop - unless it's really clogged in which case would "suck" around the valve cover gasket and grommets but i would think that would lack power big time in that case.
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'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
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Offline bootguy

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Re: Air intake / PCV valve question
« Reply #9 on: February 09, 2010, 11:29:59 PM »
Going to take pictures and post this Friday, because it is all visual to me. 
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Offline bootguy

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Re: Air intake / PCV valve question
« Reply #10 on: February 14, 2010, 11:56:44 PM »
No pictures yet due to the rain and lack of garage/carport.  Did put the parts together on the kitchen table.  It is the tube from the valve cover (#4 cylinder) to the air cleaner box that is pulling oil and coating the the large diameter rubber hose that takes the air from the air box to the TB.  took a while to clean everything, but man what a difference.  While cleaning the TB discovered a mass of melted plastic and wires.  Hope it is dry in the AM so I can take pictures and figure out what they go to.
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1994 Jeep Wrangler, 2.5L, automatic, 2.5" lift, 4:88 gearing, 33" tires, 2.5" exhaust from manifold back, air restrictor removed.

Offline dwtaylorpdx

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Re: Air intake / PCV valve question
« Reply #11 on: February 16, 2010, 08:28:38 AM »
Quote from: sharpxmen on February 08, 2010, 07:54:15 AM
he's got a '94 so i think his is in the valve cover (the brass fitting).

there's no breather, everything is behind the air filter so there's no "sucking" thru the crank/valve cover air flow path - not sure if i explained it well enough, i didn't finish my coffee yet so i might not make much sense, but what i'm trying to say is that in case your air filter is clogged and you have a breather in the valve cover then there will be a slight pressure drop behind the air filter which would result in some air going thru the breather and then thru the valve cover to the airbox - not the case with the Jeep, all the hoses are behind the air filter so they would see the same pressure drop - unless it's really clogged in which case would "suck" around the valve cover gasket and grommets but i would think that would lack power big time in that case.

Thats what I was pointing out, since the crank case vent and PCV line both hook to the intake system, If the filter plugs it starts pulling vapor the wrong way up the larger breather tube and migrates oil with it which drips down on the filter unless you have a cone filter, then its usually just in the air tube. (Depends on the plumbing...) Its worse if your at wide open throttle, since the vacuume to the PCV is pretty low.

Anyway its been a problem on my 94 since new... I keep the air filter clean and run a wire through the brass fitting every other oil change or so.

Dave

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94 YJ - 2.5 Hesco Cam B&B Ported - AX5 Trans w/Centerforce Dual Friction Clutch - 4" Rough Country Lift W/Skyjacker Shocks - D44 Rear/ARB - D30/ARB - ARB Compressor - Warn M8000 in Custom Bumper - Reunell Rear Bumper - Metalcloak 6" Body Armor Kit - Tuffy Console - 265x85-16 Tires - 2M Radio

Offline bootguy

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Re: Air intake / PCV valve question
« Reply #12 on: February 17, 2010, 12:34:03 AM »
I need to clean the tube going to the brass fitting also.  But this mass of melted wiring has got me paranoid now that I know it is there.
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1994 Jeep Wrangler, 2.5L, automatic, 2.5" lift, 4:88 gearing, 33" tires, 2.5" exhaust from manifold back, air restrictor removed.

Offline bootguy

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Re: Air intake / PCV valve question
« Reply #13 on: February 17, 2010, 12:40:20 AM »
Oh also Dave said what I was trying to get across.  Thanks.
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Offline bootguy

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Re: Air intake / PCV valve question
« Reply #14 on: March 04, 2010, 07:49:06 PM »
Quote from: Bounty Hunter on February 07, 2010, 11:34:52 PM
There is also a small inline orifice in the tube from the valve cover to the intake below the throttle body.  This orifice commonly gets clogged with carbon buildup and causes the crankcase to push oil and crankcase vapors to other places.

Is there a spray for this, or pull it out and run a wire though it?
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1994 Jeep Wrangler, 2.5L, automatic, 2.5" lift, 4:88 gearing, 33" tires, 2.5" exhaust from manifold back, air restrictor removed.
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