No CEL - not sure if limp mode but no issues before 4,000 rpm randomly
 

Hi all,

2014 Jeep JK Rubicon auto/ stock engine

so I have searched for months trying to find a solution to my problem. There are zero codes thrown, no odd sounds, no bucking or crazy idles just some small misfires due to old plugs (possibly)

tons of threads that sounds like my issue but they all have a cell light.

normal cruising around driving you’d never notice it’s interstate and passing you will notice WHEN it occurs which is very random.

I can drive over 200 miles one day and it not happen but the next day I will drive 5 miles and it will happen.

so the issue:
when hitting 4,000 rpm it will go into limp mode RANDOMLY and stay that was until the Jeep is turned off, once restarted it’s possible it won’t happen again for a day or so.

When driving and the problem is present as long as i keep it under 4,000 rpm I can get to max driving speed just slower.

In “Manuel” mode I can switch all gears as long as under 4,000 rpm.

no chance of anything if the problem
is present and I “floor it”

if I need to get up some speed quick I have to hope and pray it will not crap out. Picker factor increased.

It started happening when I had a dealer replace a rocker and bearing. After and I noticed the issue I took it to another dealer closer to me and they said everything is fine. I wouldn’t think a Jeep going into limp mode at anytime would be “fine”

Even with the bad rocker this issue did not occur and I don’t have under hood padding


things I tried:
my battery is connections are tight
air flow is clear (that I can see)
unplugged the battery for several hours
best gas I can get
The Jeep is maintained every 3,000 miles
check connections of the wiring harness

what things could cause limp mode with no cel light?


so I am at a loss, I know alot of people posted about similar things and boy do I wish their suggestions fixed my issue but it doesn’t

Similar issue
 

Hi Dj,

I just created my account with near to exactly the same problems. 2016 JKU
They car has no hesitation for the first couple of miles driven, weirdly it usually is a couple of minutes after reaching operating temp. Will not go past 4000rpm, but does still shift if you let off the gas, or when changing manually as you stated. It does feel more sluggish than usual as well.

I have had it to multiple garages, and replaced a ton under their advise;
-Rear main seal replaced
-Radiator replaced
-Rear differential gears replaced
-Upper and lower intake gasket
-Valve cover gaskets
-Timing cover gasket
-Engine oil cooler replaced
-Water pump replaced
-Trans tune up and service
-Knock sensors replaced (Did have code)

Furthermore, I have no codes but the problem persists. Have through forums read it might be due to tire size, mine is set to 35'' though I'm running 33''s currently. I will check tonight, as I'm waiting on a OBD2 programmer. Also have read on crank position sensor which might be bad, but not sure.
Hope to find some answers with you, and share my findings if any.

I dont think your issues are the crank position sensors. While u will get some random cutting out of the engine with a bad cps, itll feel more line the trans is slipping. Its a $25 part and can be changed easily enough. What it sounds like i ur cases is something with vvt system which is relates to oil pressure and higher engine rpms. Ei the engine not going above 4k. If they changes a rocker they would have had to remove the cam shaft and there is an oil control valve that bolts into the front of the cam shaft. Its activated by a solenoid that sits on the front of the valve covers. You can see two round sensors that sit on the front of the valve covers. I would say either those solenoids are bad (easy replace) oil the oil control valves bolted into the camshafts are bad (not an easy fix as you have to remove the valve cover and timing chains to replace them). But those two things are what i would look at in this case. Its odd that there are no codes. I would def code the engines with an obd2 reader.

When you guys are reporting "no codes", are you just scanning via a generic OBDII reader, or are you scanning something that can read all the modules? I can't believe the jeep is in limp mode and there is no code in the transmission module, but a basic scanner is not going to read that.

For sure! I would love to find a fix, I can definitely tell you it happened after my rocker and bearing were replaced.

I have been using Jscan and Appcar DiagFCA using the modules to see if there are codes. and haven't seen any yet even when the issue is occuring, however, the live data does show several misfires that are only detectable to the system because they are not audible.

The thing is.. don't limp mode lock you in 2-second gear? and you basically crawl home. I don't get locked in a specific gear. just can't go or 4,000 rpm

Thanks for the suggestions, I will check those once I am off call, I have been usubg Jscan and Appcar DiagFCA software.

Thanks for the info guys,

Taking ol' Hiccup to a mate's shop on Sunday, will replace the accessible solenoids and the CPS. It's low cost, but will look into the more serious repairs if that does not work.

Have a Vgate iCar pro myself, but have also have it checked at about 3 independent garages, as well as Jeep dealer in the UAE. Apart from headlight and fog lamp circuit high codes (due to LED lights and spots, the is no powertrain codes or any other.

Also have changed the tire sizes on the ECU to 32.75 (285/70/r17), but no joy yet. As Djdowney stated, I have a small loss in power, but not locked in any gear, just can't exceed 4000rpm, which is usually when going up a larger dune. The loss of power/acceleration makes it impossible to drive up

Maybe this was it?
 

So after casamtb mentioned the VVT solenoid sensors I was finally able to look under the hood and noticed the wiring harness for one of the sensors was directly touching the heater core tubes, you could tell it had been getting hot but not melted, I'm not sure if that was the issue since I haven't been able to take a drive due to being on call. But I wouldn't think its a good thing since those get really hot.. I know. I've touched them several times.

Could it possibly have been getting to hot and causing a malfunction? Just thinking out loud really. I know if I don't drive it it won't be confirmed lol

Nope, didn't fix it. guess the next thing is to replace the VVT sensors as suggested. :crybaby: Someone on another board suggested heat tape around the harness by the large harness plug that sits next to the heater tubes as well. I will try that first.

The issue is occurring more often now


-just trying to keep all my attempts in 1 thread for others as well.