I'm having trouble with my 87 YJ.  I'm getting oil blowing out of the fresh air inlet on the valve cover into the air cleaner.  I understand that it is suppose to blow excess gas back through but it's blowing oil through the fresh air inlet hose and filter on the side of the air cleaner into the air cleaner and soaking the air filter.  The air filter gets soaked with oil and needs to be changed at least once a month.  It's so much oil that it's started draining down the air inlet hose to the air cleaner.

I've checked the compression and it's between 185 and 200, which is way above the stock compression of 120 to 150.  I bought it from a guy who is suppose to be a good mechanic.  I'm not sure of what all he did to it before I got it.  When I asked him about the blow by, he told me not to worry about it that I was spending to much time under the hood and not enough time driving it.  I don't think he's trying to hide anything because he came by about six months later and asked me if I would sell it back to him.  Mabey I should have taken him up on the offer.

I've talked to other mechanic friends and they can't figure out what seems to be the problem.  I had one mechanic try and shim the plates below the PCV valve and fresh air inlet to try and get more circulation.  I've had one guy tell me to try and use the BG engine cleaner because of a possible clog in the oil line somewhere.  There isn't any kinda knocking noise coming from the engine.  I've had another guy tell me that the bottom end is gone and that's why it's blowing so much oil out the top.  He thinks I need to get a new engine for it.

I need a real answer from people who know something about Jeeps.  Is this a simple fix or is it time for a new engine or time to sell this Jeep and find one without such a large problem.

***
I need to mention that I have already put a new PCV valve in and also put all new vacum hose lines in.  So  I know neither one of those is clogged.  

Okay, you replaced PCV valve and hose so that is clear and are to sure that port it connects to is clear too? If so then you problem points to excessive blow by cause excess pressure in crankcase and blowing oil out with volume of air. You could try 15w40 oil (not 10w40) as it is a diesel rated oil and a lot tuffer that will seal cylinder better and it cleans better too. Also I do not know how you drive but keep RPM down in that do not be trying to take it to max RPM all the time. One more thing, is this lifted with big tires and stock gears? If it is this means that engine has to labor more to move load and will make a worn engine develop even more blow by on the average. Again, trying running 15w40 see if that helps and do change oil often say even 1500 miles or so for a few cycles to clean it out a bit and see if it improves.  

I have a 4.2 in my 83 jeep it started doing the same thing about a year ago I switched to 15w 40 and changed it often and it worked for a while but now i have a blue smoke exiting my exhaust still runs pretty good  though I think my problem is worn piston rings,and one cylinder is way worse than the others but if that is your only problem with that jeep I wouldnt worry about getting rid of it  just drive till it dies and then  rebuild the motor or do it now. Its just a motor as my mechanic freind tells me just fix it or put in another one. I found some remans for $1200 thats not very much to have a new source of power  

Could the fact that I have 185 to 200 on the compression have anything to do with it?  

hayman434:
Could the fact that I have 185 to 200 on the compression have anything to do with it?

Not likely but rather is it the result of engines general condition. When it starts to use some oil, carbon can build up on piston top and in chambers and that raises effective CR ratio plus old 6's tend to pump up pretty high because of short valve overlap. I know you can tend to think the with 8 to 1 or so CR that 185 is high when you do the math but not really because as you compress air it gets hotter and it expands which  makes pressure a lot higher than simple math tends to suggest.