JK 3.6 Liter - Oil in Air Filter

[MidOH]

But it runs fine?

Big tires and holding a gear at higher rpm while braking, drinks oil. Just ask anyone with a manual trans sports car, who's constantly rolling off the throttle at high rpm (high vacuum).

Replace air filter more often. Run a lower oil level. Mop out your air box as needed.

Skip the hemi, thatll just make this problem worse. And dont bother with the dealer. Blow by oil = sell new engine, same exact problem, rinse repeat.

1 qt consumption is nothing. Nothing at all.

 

[Shakes355]

PCV systems tend not to work at higher rpms on any vehicle. But Chrysler doesn't exactly put their best minds on designing their systems either.

The baffles in the valve cover are designed to provide surface area for the oil vapors to condensate on and prevent "splashing" up into the breather port. Under normal operation, enough "flow" through the system is present for this process to work (up to whatever efficiency the factory designed into it).

At high rpm, there is the combination of very little flow and higher than usual crankcase pressures. Run it for long enough in that state, and maybe factor in a sustained grade, and the oil condensate starts to accumulate in the valve cover baffles and runs right into the hose on the back of that LH valve cover. It's just an unfortunate design. This is all made worse as normal buildup accumulates in the system.

Changing the PCV valve is step 1, which you've done. I've heard the design has been improved upon, but who actually knows. Step 2 is going to be working on decarboning the system. The 3.6 has very high compression and, in turn, is very sensitive to carbon. Spark knock (detonation/pinging) is a common complaint for owners across the model range.

So I'd recommend starting with having/doing a top engine carbon service (professional or Seafoam, your call) to help clean out the combustion chambers and runners. That will give you a good base line for engine performance and *may* help with your low power complaint (the computer retards ignition timing if it senses spark knock).
For good measure, it's worth using a fuel additive every couple of tanks as a maintenance dose (techron is a solid choice that's endorsed by a few OEMs).

As far as dissolving buildup inside the crankcase, frequent and quality oil changes are the best choice. But I also have used Seafoam for many years. Sometimes as an oil additive after a fresh LOF, and other times in a higher concentration a hundred miles or so before changing the oil. Liquid oil has detergents for carbon control and the petroleum distillates in the additive help breakdown carbon as a vapor. It's a long term approach that works for most any engine.

Best of luck as you continue to diag.

 

[OTH Overland]

Now that I seem to have fully recovered from my New Years case of Covid and caught up on work, I have had some time to get back out in the shop and do some more testing/investigating. Still bugged by great leakdown results but crappy compression test I pulled the plugs again and did a retest with the same results of 100, retested the gauge and it showed accurate, but on a whim I retested the gauge as an assembly with its hose attached and what do you know it showed low, something had failed within the hose or adapter that screws into the plug hole. no matter how much pressure you put in the end gauge will not show over 100, which accounts for why all holes read the same, and low. purchased a new gauge set and retested the Jeep. This time I got a range from 165 to 170 across the six cylinders, much better and in line with the leakdown test.

While I was at it, added a bore scope to my collection and inspected all the cylinders, which all show good cross hatching, no scoring and clean piston tops. a light buildup of carbon on the face of the intake valves, but not excessive. Ran the camera down into the valve covers and anywhere else I could get it and inside of the engine looks good. Nothing I can see that would be an issue or sign of excessive wear, definitely nothing warenting a new engine at this point.

Piston Top

Intake Valve

Piston Wall


At this point I am tending to agree with @Shakes355 and a couple of others who have mentioned high rpm and load may be the cause of the oil in the breather. I did build a bracket and install a catch can in the breather line at least for the time being, this way I can keep track of miles and how much volume oil ends up going down the hose.

My attention now turns to the transmission, It has always seemed to hang on to a gear too long before upshifting especially on grades or when heavy skinny pedal is applied. Prior to our Thanksgiving trip we replaced the transmission computer with one that is supposed to correct the shifting and improve overall drivability, this did help when driving around town (nicely) but still jumps down two gears at the first sign of a hill. We went out last night to a long hill near our house and pushed it hard up the hill several times, both in automatic and manual mode. on the level the engine will run right up to redline around 6k rpm, on the hill it seems to hit the transmission computers lower rev limit of about 5k rpm and wont upshift till I take my foot off, then upshifts at too low of an rpm for power, when in manual mode and have my foot buried then try to shift up out of 2nd, the computer takes over and keeps it in second. Under full acceleration we end up redlined in 2nd or 3rd and speed is capped. a lighter foot / incline and it shifts ok and we can make full speed. Starting to think something may have gone bad or failing in the trans when we were climbing the pass in Death Valley putting the trans into limp mode rather than the engine having issues as we originally thought. Might have to take it in to a trans shop to see if they can do a diagnosis and testing on its functions as I do not have that advanced of a testing computer tool. As we do not get any slippage I would suspect an issue with the valve body.

Thanks so much to everyone who has commented through my investigation into a solution.

 

[Shakes355]

Nice find on the tester. Glad you've ruled out an internal engine problem as well.

I do have some questions/thoughts on the trans though. 2013/14 jeeps with the W5A580 had notorious programming. (Personally I think Chrysler and Ford have some of the worst on the market in general.) And there were a few bugs that make Limp Mode an unfortunately common occurrence. (One that resets after a key cycle.)

Just to confirm though, Limp Mode locks the trans in 2nd gear without any converter lockup. So you'd definitely know it if it happens. Reading your first post again, it didn't seem that was the case. That's not to say it couldn't be the trans, though.

Most manufacturers use feedback from the ABS/Traction Control (yaw rate sensor) to adjust shift points and strategies. Gears hang longer uphill and shift sooner downhill with certain brake applications. Uphill, specifically, this is to preserve the trans. Since redline shifts need to be done quickly to prevent slipping, even on flat ground, the computer will factor in grade and throttle input and stop a shift at WOT to prevent mechanical damage from the potential shock. Backing off the throttle tells the computer you're planning to slow down or crest the hill (and lowers the power output) and the upshift to OD is then allowed. See the ECU controls the throttle and thus can regulate rpm to "max out" and stop climbing- it can stay at redline indefinitely without over revving if it's programmed to.

Most of the symptoms you're describing (besides the sudden shock and power drop) are consistent with what many owners have complained about. And to my knowledge, something about those years is uniquely poor and lacking a proper fix from Chrysler.

So if you're not getting any trans codes (and corresponding dash warning lights), then I don't know what any trans shops might find for you. Especially on a trans that many consider to be quite sensitive to small issues.
Just some thoughts.

 

[OTH Overland]

Update on Eeyore's oil in air filter box and loss of power: It's been a while, but I have had some more time to work on the Jeep. Installed a catch can inline on the vent hose from the valve cover to the air box (would normally go from the PVC Valve to the throttle body) We ran a test 1,000 miles with the shifting issue as it has been and measured the volume of oil in the can (nothing made it to the air filter) and had 4oz. (1/2 Cup) which is more than I would like, but about half a quart per oil change. Since then I have reset the adaptives and baselined the transmission control module that I purchased from RPM Extreme, this has given me back manual control of up and down shifts, and for the most part allowed it to shift much better overall. still have some issues with hitting a virtual torque limit within the transmission causing the engine to reduce power at high load going up hill. Have purchased a HP Tuner module and credits and now working on tweaking the torque ramp limits for the upshifts to allow more power to be applied in 3rd and 4th. making small changes and driving for a while to see how it goes. Hoping overall this will improve shift performance and allow the engine to work more efficiently with bonus of less oil issues. At least it is more manageable to drive and do not have oil dripping out of the airbox onto the frame and ground .. lol

 

[OTH Overland]

Finally have resolved the oil in the airbox and loss of power on hills issues with our JKU:) after way to much time overthinking what could possibly be causing the issue, looking into major work or engine swap, I made on more pass through the problems creating a logic flow chart of symptoms, test results etc. I became convinced that there was some type of obstruction causing the issues, concentrating on something in the exhaust system creating excessive back pressure in the system under wide open throttle, maybe some crankcase pressure pushing oil backward through the inlet from the airbox, even blocked off the tailpipe to see if I could replicate pressure in the vent line to the airbox. Right idea, wrong end of the engine...lol. Turns out that the way Jeeps design and install the airbox it draws air in from as high and close to the underside of the hood as possible to get the best water fording ability. Great idea, but combined with a poorly executed installation of the under hood insulation blanket (and likely its material properties) results in a broken fastener and allowance of the air box inlet suction to pull the insulation down and plug off the intake, but only at high rpm and wide open throttle. The resulting starvation of combustion air causes the computer to lean out the fuel in an attempt to get the engine to run better (assuming it does not have an altitude sensor or it would throw a code) the transmission torque monitor tries to compensate from the resulting lack of power and shifts down trying to increase RPM. Once you struggle up the hill and return to normal throttle the insulation pops back up to its normal location and the unsuspecting individual looking at it later has no clue there was ever an issue. As a side bonus apparently the engine in its attempt to stave off a slow death of oxygen starvation creates a vacuum in the air box drawing its own blood from the passenger cylinder head into the filter. Offending insulation blanket has been ripped from the rest of its mounting points and is now occupying space in the trash. Fast forward to a 900 mile trip though the mountains and we are now able to accelerate over mountains, pass other vehicles, and came home to a shiny clean and dry catch can. A completely frustrating journey to find a solution, but a very satisfying and cost free final resolution. A good side effect is a thorough knowledge of the Jeeps engine, transmission and computer systems and that they are in excellent condition. Big thanks to those that have provided input and suggestions during this Journey it was much appreciated. Also big thanks to Michelle for putting up with more than a few long nights in the shop ... again ... Hope this may help any other JK owners who may run into this.

 

[AggieOE]

And now you have me wanting to work on preventing this. Thanks! Very helpful!

 

[OTH Overland]

And now you have me wanting to work on preventing this. Thanks! Very helpful!

lol... never in a million years would have guessed that would have been the issue, the fact that it would get sucked down and be solid enough to completely choke off the engine, then just pop back into place like nothing happened. Would have thought it would have been deformed, damaged or some other visible signs, and of course no codes. There is a preformed recess in the insulation just above the air inlet, I also think it may be an issue more prevalent to the Special edition JK's 10x, Recon, etc. that have the power dome vented hood, as the vents let in rain water which works its way across the top of the insulation layer and soaking it, even worse in the PNW where it rains a lot, and causes the insulation to loose some structural rigidity and eventually pulling loose from one or more of its fasteners. Not sure if I will replace the insulation, if I do I will seek some aftermarket material that is adhesive similar to sound mat, but approved for external use. For now it runs good, with only slightly more engine noise in the cabin, but I did not purchase the Jeep for its tranquil acoustics in the cabin lol.