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Unread 02-17-2012, 05:11 PM   #1
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1989 YJ Wrangler 
Join Date: Jun 2011
Location: Frisco, Il
Posts: 1,377

Today I was looking at the top end of the motor for any oil leaks that would drip down and make it look like an RMS leak. Good news is that I don't, but here's the bad news.

I took the air cleaner off and inside was a small puddle of a gassy/oily liquid that didn't look good and my air filter is soaked with this liquid. This is my first jeep and I have never encountered this. Please, I need help, what could cause this. What is the problem?

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Unread 02-17-2012, 05:20 PM   #2
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1988 YJ Wrangler 
Join Date: Nov 2009
Location: Pinion Hills, Ca
Posts: 7,684
That's blow by bud. I have the same thing along with a little water in the oil. I've read that you have to clean all of the breather system but I haven't had the time/patience to tear it all apart yet.

Louie here said that's what he did. And another guy said he had to clean the baffles under his valve cover as well. If you find a remedy other then that or a catch can please share.
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Unread 02-17-2012, 05:25 PM   #3
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1993 YJ Wrangler 
Join Date: Feb 2009
Location: Colorado, Colorado
Posts: 363
try changing your pcb valve
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Unread 02-17-2012, 06:24 PM   #4
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1989 YJ Wrangler 
Join Date: Sep 2008
Location: Colorado
Posts: 413
Hi Colliin, here are four links which youíll find helpful I suspect. If youíre getting oil in the air cleaner assembly you probably have problems with the PCV system. Get a new PCV valve, about $4 or so and check the hose from the valve to the back of the carb at the base. Make sure itís clear and that the inlet on the carb is clear as well. There originally was a solenoid valve in the PCV line physically located between the carb and the head which was designed to block gases from flowing at idle; this was recalled later and removed. If you still have it then run a hose straight from the PCV valve to the carb connection. You can leave the solenoid connected to itís electrical plug and just tuck it away somewhere because itís neutralized, or unplug it and put it in your box of stuff.

Read the topics in the center column of the third link regarding setting the carb idle. The factory settings for the mixture screws is 2.5 turns out from a gently seated bottom. Both screws are set equally, so thatís a good starting point. If you want to tune it then the Best Lean Idle method is a good way to go. Connect a vac gauge to manvac. (If you still have all the emissions equipment, disconnect the larger manifold vac line from the vac reservoir under the battery and plug the gauge in that; this will also neutralize the Pulse Air and Solvac systems while youíre tuning which is a good idea.) With the engine at operating temp and idling, turn both mixture screws in 1/8 turn, bump the throttle a little and wait 15 seconds before doing it again; continue until you reach maximum vac reading and then back each one out 1/8 turn and youíre done.

If you want to verify your tune, put a multi-meter in line between the O2 sensor and itís connection. You should have about .6 volts (+/- .05v) at idle; .1v is lean and .9v is rich.

Hereís the links:

How to read a vacuum gauge:

How to read spark plugs:

Whatís under the hood:

Carter BBD Factory Service Manual:

If you wish to rebuild the carb itís easy and the rebuild kit is only about $20, BBD model 8384. Just make sure that you soak it generously with spray carb cleaner (get one with a spray tube on the can to blast it into the channels), let it soak for a 30 minutes or so, blow all of the channels out thoroughly, and then repeat the procedure. Make sure the venturi tubes are clear and that all of the tiny holes in the venturi cluster are clear (use a fine brass or copper wire if necessary.) During reassembly lightly grease (axle grease) the cup that the accelerator pump seats in and make sure that the larger ball bearing goes in the cup. The smaller ball bearing is in the venturi cluster.

As to vacuum readings for manvac, a healthy engine with no vac leaks should be around 22" HG at sea level. Subtract 1" HG for every increase in altitude of 1000 feet. Iím at 9000 and read 15" HG.

I hope this helps. Let us know how it goes.
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Unread 02-17-2012, 07:01 PM   #5
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1991 YJ Wrangler 
Join Date: Dec 2010
Location: 14304 Niagara Falls, NY
Posts: 2,537
Collins89 -
That's just the usual condensation. Its caused by the fumes in the crank case, if your breather syspem is clogged or if your vacuum isn't tight. Mine used to do that every month till I totally cleaned the breather system, replaced a couple hoses, and generally made sure everything was totally air-tight. It tends to happen more in the winter time since the outside air is colder. It also happens if the engine doesn't get good-n-hot. BUT it'll happen anyway if your system is clogged or leaky. Hope that helps.

UnFocused: That is an *awesome* post, I cut-n-saved it!
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Unread 02-17-2012, 07:43 PM   #6
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1989 YJ Wrangler 
Join Date: Sep 2008
Location: Colorado
Posts: 413
Thanks Oldtime, I just cut and pasted it from a Word doc I've got. I seem to post it monthly, after tweaking the intro if necessary, on some thread either here or in the CJ forum as the late CJ7's are all but identical to the 87-90 YJ's. It's just something I've condensed over the past 3 years or so. Didn't have to tweak anything on this thread

Always lots of new folks showing up, many young, fewer and fewer understand carbs anymore. I simply decided to post a "boiler plate" response which provides a base for Old School diagnostics, a little education, and hopefully answers to questions not yet recognized or documented in the links.

Today's world of taking your car to the dealer so their computer can talk to your computer is the norm. Inconvenient and expensive, but still the norm. But the Old School approach is fully applicable to modern engines. One should always be able to find manvac somewhere, spark plugs ... well maybe.

Thanks again
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Unread 02-17-2012, 07:57 PM   #7
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1990 YJ Wrangler 
Join Date: Feb 2012
Location: Madison, AL
Posts: 20
Mine has blowby too but it was explained to me as a compression ring problem that was over-pressurizing my crankcase, causing the PCV and carb to not be able to process the excess pressure and as a result it sputtered oil into the air cleaner. I have removed my solenoid too and I have a new carb but have not checked the hose from the PCV to the carb to see if it's sucking. I just resigned myself to a new air cleaner every month or so. I have some new things to check now, thanks!
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