Jeep Wrangler Forum

Jeep Wrangler Forum (
-   YJ Tech Forum (
-   -   air box full of (

bizzleyj 05-29-2008 09:24 PM

air box full of
i jus purchased a 91 wrangler has the 2.5 and the hose from the valve cover that goes to the air box is spitting oil in there,,does any one know ylllll

Triple88a 05-29-2008 09:41 PM

is it clogged? Pull the breather pipe out and check it out. I have the feeling thats its clogged and there is just a small hole left so it sucks the oil up.

crafty 05-29-2008 10:43 PM

With any luck it is something minor. I had a 92 before with a 4cyl that lost compression due to being worn out. One of the engines I tried to replace it with had severe blow-by. Pumped it into the airbox, up the dipstick tube never seen 1 that bad. Rebuild time or NEW engine if it is not something minor :( Don't waste your time with salvage yard engines like I did. 4 times to find a descent engine in the salvage yard, not worth it IMHO.

A little oil can be considered normal.

AzTJ 05-29-2008 11:17 PM

Check the PCV valve that the hose is connected to on the top of the valve cover. When they go bad they let blow-by through.

Triple88a 05-29-2008 11:22 PM

Az, isnt the PCV all the way back by the firewall?

Dare2BSquare 05-29-2008 11:43 PM

Yeah, that's just a crankcase ventilation hose.

Triple88a 05-29-2008 11:54 PM

i've been wondering that for a while. Whats the difference between the pcv and the breather one. On my old vehicle (havent messed with it on the jeep yet) it was connected to the intake manifold so this tells me that when i let go of the gas it gets vacuum but i dont know if thats right.

AzTJ 05-30-2008 12:31 AM

Older Jeeps have PCV valves and newers don't, instead they have a CCV or crank case ventilation which is just the rubber grommet with a small orifice.

To check the PCV, remove it from the valve cover and shake it. If it rattles, it's not clogged. Then with the engine running, put your finger over the bottom and you should feel it sucking.

bizzleyj 05-30-2008 11:27 PM

i installed a snorkel yesterday and just ran a hose from that valve cover breather under the frame so it dosent spray oil everyware,,

Triple88a 05-30-2008 11:41 PM

what do you mean? the breather is suppose to be connected to the intake so the harmful fumes produced inside the engine can be "vented" into the intake and then burned in the combustion chamber.

parrot head 06-01-2008 06:38 AM


Originally Posted by bizzleyj (Post 233320)
i jus purchased a 91 wrangler has the 2.5 and the hose from the valve cover that goes to the air box is spitting oil in there,,does any one know ylllll

Check all your vaccuum lines for blockage, especially the metal ones. When I bought my yj 4banger it had the same problem you are describing. It ended up being severely plugged up vac lines.

rebelBullDawg325 06-01-2008 07:57 PM

its a blow by issue. not pcv valve. i've seen 2 91 6cyl do the exact same thing first hand.... on mine i just disconnected from the air box, plugged the hole on the box then lengthened the hose to where it hangs real low and the excess oil drips out. my buddy re routed his hose closer to the throttle body so it would burn it up in the combustion chamber

4.0l sahara 06-01-2008 08:29 PM

Some times a clogged pcv valve will cause oil to be blown out the breather and seem like blow by even know it isn't. Try replacing the pcv valve.

lonerider6 06-24-2008 08:58 PM

oil in airbox
I had the same problem with my 95 2.4l. The CCV system was not working properly. I removed the small brass fitting on the left side front of the valve cover and found the very small orifice in the fitting was totally blocked with yeek. The flexible hose that connects the fitting/orifice to the plastic vacuum tube that then connects to a fitting on the intake manifold under the TBI was also shot and creating a major vacuum leak. I removed all the pieces, cleaned them all with carb cleaner, ran a small brass bore brush through the fitting in the intake manifold under the TBI, replaced the flexible hose and clamped it to both the orifice/fitting and the plastic vacuum tube. That solved the vacuum leak problem quite nicely and no more oil in the air box. It also seems to have increased the fuel mileage slightly. I think this is an often neglected bit of maintainence and I am sure that mine had not been cleaned in 135,00 miles.

Buc Knaked 06-25-2008 01:14 AM

mine does the same thing but i was told that they just did that when it was an overflow and it was normal for there to be some oil.

parrot head 06-26-2008 06:54 AM


Originally Posted by xxcheathamxx (Post 240383)
mine does the same thing but i was told that they just did that when it was an overflow and it was normal for there to be some oil.

no, not normal. It is either blocked vacuum lines, pcv or blow by. This just me, but I'd check all the cheap and easy stuff that was mentioned here before I just gave up and said it was blow by. In my case it was the steel vacuum manifold that was so plugged when I bought my 89 4banger that I had to remove it and let it soak in solvent overnight before blowing it out with compressed air. After that, no oil in the airbox:doh:

Davers87 05-25-2013 12:32 PM

I think I just fixed this on my jeep yesterday. Took off the valve cover, cleaned all the sludge caked inside around the valve cover was probably a quarter of an inch thick layer all around pretty bad but I shouldn't have to do it again for a long while. The sludge was blocking the front pcv valve and so the back valve was working as a vacuum pulling oil into the intake.

All times are GMT -5. The time now is 05:50 PM.

User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.