[2012JKU]

Dead spot at 1500 RPM on new 3.6? (Edit: Solved?)

I recently bought a 2012 JKU auto and I've been enjoying driving it, except for one thing. When I'm rolling down the road at 40-50 MPH and 1500 RPM and decide to speed up some, it seems resistant to increasing RPM. It almost feels like the engine doesn't know what to do. You can feel it wanting to increase, maybe downshift, it just seems conflicted. If i give it a significant amount of throttle it'll downshift and speed up. Has anyone else seen this?

 

[2012JKU]

Nobody else.seeing this? Maybe I should take it to the dealer for a.reflash

 

[gold knight]

Sorry you're part of the new minority 12+.

 

[2012JKU]

Yeah, I was just hoping it was normal behavior. I wonder if the dealer swapped wheels and tires and its throwing it off

 

[oz97tj]

I didn't notice that with mine. My had 3.21 gears and my 35s went on basically as soon as I got home so it was a bit sluggish then. I then calibrated the computer for the tire size and felt no issues like that. Now I've swapped to 4.88s and still feel no dead spot, although it isn't exactly at 1500 rpm all that often.

 

[2012JKU]

I think its time to take it to the dealer. Make sure its right before I put bigger tires on it so they don't blame it on that

 

[JKCTAZ]

Could be a behavior with the drive by wire throttle. I notice in my 2011 during "Eco" mode that the rpm and engine sounds oscillate (at a similar RPM) even if I have a steady foot position. Then, getting out of Eco mode seems laggy. Not sure if the Pentastar employs an Eco mode, but could be the same behavior.

 

[2012JKU]

Could be a behavior with the drive by wire throttle. I notice in my 2011 during "Eco" mode that the rpm and engine sounds oscillate (at a similar RPM) even if I have a steady foot position. Then, getting out of Eco mode seems laggy. Not sure if the Pentastar employs an Eco mode, but could be the same behavior.

It does have Eco mode. Its in it when its cruising at 1500. Sounds like the same thing. I bet you cant disable Eco mode can you? At least until aftermarket Ecu tools are available.

 

[JKCTAZ]

As far as I know, no, you can't disable it. Then again, I have never opened the manual on disc (who puts the manual on a CD for A vehicle that is supposed to be used in the middle of nowhere?) so I can't be certain. Sounds like the same behavior. If I really romp the throttle then it goes, but it's irritating at times when I just want to increase my speed by a few MPH to go around someone on a city street. Just figured it was part of the "charm" of this vehicle.

 

[oz97tj]

My '09 didn't have an Eco deal but the motor and all is the same in the '11 so I'm guessing it's just reading load on the motor and the fuel consumption used.

However, on the '12s, as I understand it, the Eco deal has to do with the VVT. Basically, under no load the motor runs the valves one way and under load it opens them another way to allow a bit more power. This is the most basic way to explain it anyway. lol

Either way, I've never really noticed much difference in mine so you may have something going on.

How many miles are on it? What gears? What size tires?

 

[2012JKU]

700 miles, 3.21 gears, 255/75/17

 

[2012JKU]

Took it to the dealer today. There's a bulletin about it, and they have updated firmware to improve the shift points and several other issues. On the drive back from the dealer it definitely performed as I always expected it to, with no more hesitation or shift confusion.

 

[jeepchic55]

Way to be proactive! I bet you have saved a few people a headache about it.

 

[bo9roadking]

Took it to the dealer today. There's a bulletin about it, and they have updated firmware to improve the shift points and several other issues. On the drive back from the dealer it definitely performed as I always expected it to, with no more hesitation or shift confusion.

I'm glad you made a post about this. I'm going to make an appointment with my dealer to see if I can get the updated firmware. I have a similar issue with my 2012 JKU that I purchased in August. When I take off from a stop, the engine feels like it hesitates at about the same rpm that you mention. The engine rpms climb as I take off from a stand still, but then it acts like the engine is stalling out or hesitating briefly. It doesn't sputter, it just acts like it lost power for a microsecond. I wind up giving it more gas to get it past that rpm range because it acts like it isn't sure what to do. The extra gas pedal gets my JK past that rpm and then it shifts.

 

[2012JKU]

I'm glad you made a post about this. I'm going to make an appointment with my dealer to see if I can get the updated firmware. I have a similar issue with my 2012 JKU that I purchased in August. When I take off from a stop, the engine feels like it hesitates at about the same rpm that you mention. The engine rpms climb as I take off from a stand still, but then it acts like the engine is stalling out or hesitating briefly. It doesn't sputter, it just acts like it lost power for a microsecond. I wind up giving it more gas to get it past that rpm range because it acts like it isn't sure what to do. The extra gas pedal gets my JK past that rpm and then it shifts.

Mine had that also. Doesn't seem to be there anymore. The guy at the dealership said it should take about 500 miles or so to fully relearn everything, and I'm only about 100 miles in, but it's sure a big difference. Glad to have helped and to have found that it isn't just "jeep character".

 

[bo9roadking]

Mine had that also. Doesn't seem to be there anymore. The guy at the dealership said it should take about 500 miles or so to fully relearn everything, and I'm only about 100 miles in, but it's sure a big difference. Glad to have helped and to have found that it isn't just "jeep character".

I'm taking my Jeep to the dealership today. When I made an appointment to have it checked, I mentioned what you had said about a service bulletin. The service tech said that he didn't know anything about it and couldn't tell me anything more until I brought my Jeep to them and they could input my VIN into their computer system. I should know something later this afternoon.

I hope my dealership is on top of their game like you dealer was and that they will find the bulletin and update my Jeep's computer. The sales staff at my dealership has been fantastic. This will be my first trip to the service department, so I'll soon discover how well that part of the dealership operates.

 

[bo9roadking]

Mine had that also. Doesn't seem to be there anymore. The guy at the dealership said it should take about 500 miles or so to fully relearn everything, and I'm only about 100 miles in, but it's sure a big difference. Glad to have helped and to have found that it isn't just "jeep character".

I just got back from getting my oil changed and having the dealership look into the engine/transmission not seeming to know what is going on for a brief period. The service tech said that there weren't any service bulletins or firmware updates for my Jeep. He said the mechanic took it out for a test drive and did notice what I was talking about, but that without a service bulletin, firmware update, or check engine light, there is nothing that can be done. When I mentioned that someone on the jeep forums had the same issue fixed at their dealer, my dealer said that isn't possible and that the other dealer was blowing smoke.

The mechanic said it might be my 35" tires, since they aren't the stock size. I've already adjusted the shift points using the AEV ProCal, so that should eliminate the larger tires causing any problems. The only thing that I can think of is that once the transmission shifts gears that the rpm's drop enough to get out of the higher torque band and causes a slight hesitation until the rpms increase a bit. When I give it more gas, it gets moving again. It isn't a major issue, just an annoyance. Now that I have my cat-back exhaust, the louder exhaust makes it more noticeable because I can hear the hesitation now in addtion to feeling it.

I think that I will disconnect my battery for a bit to reset my computer. I've done a lot to my jeep in the last 3 months and maybe the computer needs to start over to get adjusted to my mods. If your dealer did something to cause your jeep to start relearning your driving habits, maybe I need to reset my computer to do the same thing and wait up to 500 miles for the results.

 

[2012JKU]

either your dealer doesn't know what's up or mine lied, then. Toss up either way but I know whatever they did sure fixed mine.

 

[oz97tj]

Depending on date of manufacture, you could already have the updated programming which is why they couldn't find any updates.

You mentioned you have larger tires. This will affect the way things work even if you have the tire size adjusted via procal. It's still likely geared to high. What gears do you have?

I'm having an opposite issue on mine. I have regeared my '12 to 4.88s. I'm running 35s and have reprogrammed with a ProCal. My problem is it wants to hold 3rd and 4th gear to about 4000 rpm on every shift, even when accelerating slowly. It also will hold the gear, turning 3500 to 4000 rpm without upshifting when maintaining a steady speed. I have to lift my foot off the throttle for a second to get it to shift, or manual shift. I've called AEV twice now and left messages, but I still haven't gotten a call back. I'll try again Monday.

 

[jvandy50]

It will be interesting to see if more people experience this. Had a motorcycle that had a stall at 2500 rpm an after enough people noticed it and found the thread, Yamaha started replacing the bad computers. Good luck in getting it figured out


Vandy