Jeep 4.0 has a CCV system, not a PCV system. You are probably experiencing some BLOWBY, a relatively common problem, especially on your vintage XJ. I had it on my 88 Comanche but it is really pretty easy to manage and it doesn't necessarily mean your engine is on its last leg. Use the SEARCH function for information on BLOWBY; no need to reinvent the wheel here. Good Luck!
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche Without "data", all you have is an opinion!
Along with the updated CCV parts, you could also switch to a late 4.0L valve cover. It has some revised baffling to help keep oil out of the CCV lines.
x2 If your lines are clogged, you will deff. get oil in the air filter. and it's not really blowby. I had an oil soaked air filter last year, bought new lines and elbows from the factory (around 30 bucks). and havent had any oil in there since.
'95 XJ country edition, 4" coils/3/4" spacers, HD leafs with extra main added in, Ironman adjustable control arms, rough country shackles, aussie locker, JK rubicon shocks, 35" mudder's, soft 8's, cobra cb
Sold '00 TJ, 4" lift, rusty's adjustable control arms, skyjacker shocks, rock krawler adj. trac-bar,rugged ridge SYE and RE driveshaft, soft 8's, 35" mud king xt's,XJ HP D30 w/aussie locker, 4:88 yukon gears, hella 500's, rock crusher diff covers
4. 04 Dodge ram 1500 quadcab, yes, it has a hemi.
5. '08 BMW X3, Mods in progress.