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blow by

fristjeepguy

NAXJA Forum User
i've been told i have blow by on one or more of my pistons in my 4.0L is there a permant fix to this. i've been told this is very common. is there some kind of performance ring that will make sure this won't happen again?

SCOTT
 
Are you talking about oil in the air filter? If that is your problem I may have the fix for you. I took off the stock PCV system and went with a basic PCV valve system. I have all the part numbers at home and can take pictures if needed. let me know if this is what your problem is.
 
I´ve had what appeared to be blow by, disapppear when the crankcase ventilation system was cleaned.
What year XJ? A compression test showing low compression in a cylinder or two, can be a tip off, some oil/compression rings are worn or lost temper when the motor overheated at some time.
 
Coop said:
Are you talking about oil in the air filter? If that is your problem I may have the fix for you. I took off the stock PCV system and went with a basic PCV valve system. I have all the part numbers at home and can take pictures if needed. let me know if this is what your problem is.

there is no pcv. its a ccv system and i would stick with the dealer replacement. there are a million posts about blow by
 
Just to clear it up wether I call it PCV or CCV it is the same thing. It is crankcase ventilation. Both the "PCV" and "CCV" system work in the same way. The only difference is the system on the 4.0l uses an orifice to regulate the amount of vacuum and the other uses a PCV valve. The problem on the 4.0l is that the vacuum is insufficient for removing the gases through the tiny orifice and vacuum line. The system as designed can not handle even normal blow by of an engine with average wear. The mod that I made works well and does not cause any running or drivability problems what so ever.
 
1. Can you actually replace the stock snorkel/plate/rubber pcv grommets with an actual valve/grommet combo?

2. My father in law though that I could just detach the hose causing the problems at the air filter and run it (with a filter at the end) to frame rail (thus no more oil in the air filter). I said that hose is part of the vacuum system- he disagrees. HELP!!!
 
Somebody on this forum has replaced the early Xj ccv system with a late model setup and solved their problem. Search the forum.
 
If you just taking it out of you filter housing and putting a filter on the fresh air line from the air cleaner will not solve the problem. All that will do is cause the blow buy to cover your engine where ever the new filter is mounted with oil. The problem is the vacuum side is inefficient at removing the gases. I will post my fix here tonight so check back tomorrow (I have all the part numbers of the items I used).
 
There is a Tech service bullieten for this problem. I had you install a new orfice tube. It came with an improved grommet for the valve cover and the tube was bent differently.

The improved tube has it so the first 90 degree bend over the intake is higher than the rest of the run of the tube. This prevents crankcase stuff from collecting.

Install the new tube and you will most likely fix the problem.

Now flip around your air filter and drive for 2 weeks, monitor the oil on the filter and if i has a little at first which is left over from the system running backwards then you are fixed.

I never saw this posted other than by me but if that does not fix it then have your cat converter replaced. It prob stopped up and making back pressure.

I just replaced all the CCV tubes on my 88 XJ yesterday as part of my 150,000 mile tune up.
 
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