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just floor it!
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Discussion Starter · #1 · (Edited)
OK I just got this thing and every now and again when its idleing it will idle way down and almost die, usualy you can catch it and hit the gas, but it really isnt norm, at least i dont think that. It has 156xxx mile's on it.

Thanks in advance to any advice i get.:confused:


Ok now that i cleaned the throttle body and tps, i left the intake tube unhooked from the air box because the air filter was soaked in oil? That did make a difference in the idle prob, it dosnt come as close to stalling as when the tube is hooked up, i tried both ways.

Now the new question is where did all that oil come from? was it the pcv valve or one of the other 100 hoses that connect to the airbox? the valve cover has one hose that connects to the airbox and it comes from the front of the valve cover, i didnt see a pcv valve in that hose, but that had a major amount of oil in the collector(which is a ribbed sleeve inside the airbox tube) removable of course. so now im lost as of what to try next.
 

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Idle speed solanoid on the throttle body. Maybe clean it.
 

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I had my idle speed circuit fail before and it fails to low RPMs. I had a spare throttle body sitting around so I cannibalized the one from it and have been fine for the last 6,000 miles or so.
 

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Premium Member
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The 88-90 is different than anything else because it's a Renix motor, different electronics. I had a similar thing with mine, turned out the TPS needed to be cleaned up and adjusted. You can do it with a multimeter.

There's step by step instructions on this at NAXJA.org
 

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just floor it!
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Discussion Starter · #6 ·
I will try cleaning the tps and the whole throttle body, i will let ya know, thank guys.
 

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those motors dont have a pcv valve on them, the crankcase ventalation runs through the valve cover, and it gets clogged, which needs to get cleaned out. i still need to do that with mine
 

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just floor it!
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Discussion Starter · #9 ·
Fraser

How do i do that, is it hard or easy?

Does yours have a lot of oil that gets into the air filter?
 

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I am the law.
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Its easier to troubleshoot problems if you keep the information posted in chronological order through the thread.


You have blow-by. Your crankcase is being pressurized by it and its pushing oil through the tubes you found into the air box.
 

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just floor it!
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Discussion Starter · #11 ·
Sorry i will remember that for next time.

should i do a comresion check? and just change the air filter then see how fast it gets oily?
 

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A-1 Dave Costa
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my 88xj had the same blow-by problem, and since it is only a wheeler, i rerouted the CCV into the charcoal canister and put an open cone on the intake...
 

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just floor it!
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Discussion Starter · #15 ·
OK I put an open cone filter on it and rerouted the hoses that went into the air box, it idle's a little better, but now i am finding an oil leak that is coming from the back of the oil pan-front of the inspection plate, and only when running, after it is shut off it does not keep leaking. Is that the rear main? if it is, is it a two piece or one peace main?
 

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You have blow-by. Your crankcase is being pressurized by it and its pushing oil through the tubes you found into the air box.

Blow-by is caused by gases getting past the rings and causing a high pressure in the crankcase which then finds it's way out through the valve cover vents.

Most 4.0L's do not have a blowby problem they have a plugged CCV system. Idiots from back in the day wrote an article on the problem and said it was blowby but it's not. Cleaning the CCV system and possibly replacing the tubes will cure 99% of oily intakes. The small tube gets clogged up and can't ventilate properly and the big tube becomes a huge vacuum hose and literally sucks oil into the airbox. You may have to pull the valve cover off and clean up under there to get it to go away.

http://jeep.off-road.com/jeep/Engin...Article/detail/257985?contextCategoryId=34170
 

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OK I put an open cone filter on it and rerouted the hoses that went into the air box, it idle's a little better, but now i am finding an oil leak that is coming from the back of the oil pan-front of the inspection plate, and only when running, after it is shut off it does not keep leaking. Is that the rear main? if it is, is it a two piece or one peace main?

2 piece rear main so you have to pull the oil pan.
 

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Blow-by is caused by gases getting past the rings and causing a high pressure in the crankcase which then finds it's way out through the valve cover vents.

Most 4.0L's do not have a blowby problem they have a plugged CCV system. Idiots from back in the day wrote an article on the problem and said it was blowby but it's not. Cleaning the CCV system and possibly replacing the tubes will cure 99% of oily intakes. The small tube gets clogged up and can't ventilate properly and the big tube becomes a huge vacuum hose and literally sucks oil into the airbox. You may have to pull the valve cover off and clean up under there to get it to go away.

http://jeep.off-road.com/jeep/Engin...Article/detail/257985?contextCategoryId=34170
sorry about my late resonse, but theres the answer right there:thumb:
 

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Let me add something to Motor Slut's post. Not only will the oil come out the valve conver vent...but also the dipstick tube. I know this from personal experience with my old Jeep engine. To test this pop your hood and fire up your engine. Put it in neutral and place a weight (I used a sledge hammer) on the gas pedal to get the revs up to 4 or 5000 rpm. Then take a look at the dipstick tube. This would result in oil in the place you mentioned...so you might not actually have a leaky main seal.
 
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