Oil in the airbox...no CCV

90growler

90growler

New member
According to my haynes manual and other threads that I have read, oil in the airbox is caused by a clogged CCV valve. My model does not have one. The PVC Valve is sucking like it should, but the vaccum line from the valve cover to the airbox is blowing in reverse. I cannot figure out why..........I have replaced the valve and the line and got the same result......has anybody had this problem???????this is a throttle body injection 2.5L so the lines are a routed different than the '91-'95 YJ. Does anybody have a TBI that has encountered this????
 

The small vacuum line to the front of the valve cover is likely clogged, does it have a brass fitting screwed into the valve cover? Check it for a small orifice that is likely clogged with carbon.
 
You'll get oil in the airbox (coming up from the pcv valve) if you have worn rings, worn cylinder walls, or anything else like that.
 
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ive heard it to be a design flaw that not much can be done about than to repeatedly replace the airfilter. ive had brand spankin new pcvs blow back on me.
 
You will continue to get the oil IF the CCV is working properly and the manifold is sucking properly from the valve cover. This sounds like a blowby condition. If the CCV is clogged and has less than required vacuum into the manifold, it could be the cause.
 
I don't think my model has a CCV. I looked for it, and I cannot find. My manual only says that some later model Yj's have one. Is that right?? This is a 90 with the TBI. Define blowby. How is it resolved?
 
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You have either PCV (positive crankcase ventilation) or CCV (closed crankcase ventilation), and FI vehicles generally have the CCV (at least FI jeeps that I've dealt with).

Both deal with air into the crankcase from the airbox, and crankcase vapors into the intake to be burnt. The PCV uses a 1-way valve at the valve cover, the CCV does not. The CCV has a small orifice somewhere inline with the vacuum hose from the intake manifold to the valve cover, this orifice is commonly clogged with vacuum.
 
I have the PCV system according to Haynes.....This is what part of it reads.

If abnormal operating conditions (such as piston ring problems) arise, the system is designed to allow excessive amounts of blow-by gases to flow back through the crankcase vent tube into the air cleaner to be consumed by normal combustion.

Sucks.....I guess this means I have ring problems? I guess that is to blame for all the black stinky crap shooting out of my exaust pipe. Is this something that I should get taken care of immediately? The motor does not consume or burn any oil.

what if I just pull the hose out and let it blow somewhere outside the airbox?
 
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Bounty__Hunter said:
I've read of jeepers running the hose to a catch bottle, and dumping it out occasionally.
Click to expand...

dumping it out? what kinda jeeper throws things away? dump it back in :purple: :lol: :purple:
 
Get a K&N Filter and wash it regularly.
I had a 93 Grand with the 4.0 and it put oil in the air filter housing from day 1. I never looked into the problem, just thought it was a design flaw. The engine ran great, never used or burned oil. I just kept the air filter changed regularly.
 

How do you get so much oil in the air filter, yet it never checks low?
 
redrooster said:
Get a K&N Filter and wash it regularly.
I had a 93 Grand with the 4.0 and it put oil in the air filter housing from day 1. I never looked into the problem, just thought it was a design flaw. The engine ran great, never used or burned oil. I just kept the air filter changed regularly.
Click to expand...


Ya, That's what I did too. Just put a regular replacement K&N on there and washed it all the time. My airbox would have a big puddle of oil in it after only a couple weeks
 
Update: I disconnected the line from the valve cover to the airbox for experiment. Makes a huge difference. No hesitation and more response. My jeep wasn't putting allot of oil in the box just a bunch of smoke. I do have a K&N so that is no problem, but I think I am going to connect that hose to a container and dump it once in a while. THere has to be some sort of flaw in the PCV system. That must be why they tossed it and went to CCV. It seems over sensitive. Any other suggestions,this is what the PCV system looks like:

image-missing.png


where it reads Air In on the back of the valve cover is where mine is flowing backwards
 
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