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Hi there, bought my first jeep last November 2018 and have put in a lot of miles on it since (about 20k) not super hard miles just around town with a couple trips up the snow early in the year.
currently I am experiencing an issue when exceeding 37 mph and approaching a stop light or sign I press the breaks and as I go through the range of 25-18 mph my car lunges forward as it slows down. Almost feels like it accelerates slightly as I’m slowing down. That is the best way I can describe it. Looked around and haven’t seen a whole lot on what I’m experiencing, any input would be greatly appreciated.
 

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Hi there, bought my first jeep last November 2018 and have put in a lot of miles on it since (about 20k) not super hard miles just around town with a couple trips up the snow early in the year.
currently I am experiencing an issue when exceeding 37 mph and approaching a stop light or sign I press the breaks and as I go through the range of 25-18 mph my car lunges forward as it slows down. Almost feels like it accelerates slightly as I’m slowing down. That is the best way I can describe it. Looked around and haven’t seen a whole lot on what I’m experiencing, any input would be greatly appreciated.
Hi meuni011,
Are you considering having your dealer take a closer look? If you decide to go this route and would like additional assistance throughout your dealer visit, please send us a PM. We'd be happy to connect you with a Case Specialist.
Alex
JeepCares
 

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Does engine RPM jump up as it lunges forward?

Try slipping into neutral as you slow down. See if it still lunges forward or if the engine revs up as you hit the same point during slowing down....
 

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sounds like an issue i had as well. look and see what gear it is in and shifting to when it happens. Mine always did it when it would shift from 5th to 4th.
 

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I have the same "issue" MY15 Summit 5.7. Its almost as if the electronic assist on the Brakes readjusts and you're forced to use more pressure. Which makes for a not so smooth stop. Im curious what your dealer says if you bring it in.
 

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sounds like an issue i had as well. look and see what gear it is in and shifting to when it happens. Mine always did it when it would shift from 5th to 4th.
i just tried this and it does not jump forward like it does while in Drive. What does this mean?
 

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Discussion Starter #7
I have the same "issue" MY15 Summit 5.7. Its almost as if the electronic assist on the Brakes readjusts and you're forced to use more pressure. Which makes for a not so smooth stop. Im curious what your dealer says if you bring it in.
I’ll keep you guys posted on my findings. Taking it in next week
 

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I have the same "issue" MY15 Summit 5.7. Its almost as if the electronic assist on the Brakes readjusts and you're forced to use more pressure. Which makes for a not so smooth stop. Im curious what your dealer says if you bring it in.
? Electronic Assist on the Brakes? The brakes work purely hydraulic between pedals and pads for normal stops... ABS only comes just as wheels lock-up and maintain threshold braking, which is extremely heavy max braking.... ....the ABS will activate at individual wheels for ESP/Traction Control/BTCS, etc which if its dry weather during normal braking this should not be coming on.....

The brake booster works off vacuum, a loss of vacuum could cause a loss in brake boost and require greater force on the pedal for the same amount of braking power. But even that only changes as you change the pedal position, unless the vacuum leak is in the booster itself....
 

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? Electronic Assist on the Brakes? The brakes work purely hydraulic between pedals and pads for normal stops... ABS only comes just as wheels lock-up and maintain threshold braking, which is extremely heavy max braking.... ....the ABS will activate at individual wheels for ESP/Traction Control/BTCS, etc which if its dry weather during normal braking this should not be coming on.....

The brake booster works off vacuum, a loss of vacuum could cause a loss in brake boost and require greater force on the pedal for the same amount of braking power. But even that only changes as you change the pedal position, unless the vacuum leak is in the booster itself....
I assumed it was electronically assisted do to the fact of the trucks Slows itself down when using adaptive cruise control. Unless the ABS is controlling that her which is electronically controlled.
 

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sounds like an issue i had as well. look and see what gear it is in and shifting to when it happens. Mine always did it when it would shift from 5th to 4th.
i just tried this and it does not jump forward like it does while in Drive. What does this mean?
? Tried what? Rasull said he watched the gear indicator and notice the symptom happens when the trans shifts from 5th to 4th gear. What did you try that resulted in the symptom NOT happening while slowing down?.... ....looking at the shift indicator doesn't effect how it shifts....

Engine braking can contribute to your deceleration, if the engine braking changes that would change the deceleration.....
Usually with the Auto Trans in drive, it doesn't create enough engine braking that a change in it would make any noticeable difference.....
Throw on top of that, shifting from 5th to 4th should cause increased engine braking, not less, if anything the vehicle would decelerate more when downshifting gears....
So something is wrong, as in a malfunction, in Rasull12's scenario, the only thing I can think of at the moment, the Electronic Throttle Control malfunctioning and opening up the throttle during downshifting.......
 

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I assumed it was electronically assisted do to the fact of the trucks Slows itself down when using adaptive cruise control. Unless the ABS is controlling that her which is electronically controlled.
I don't have Adaptive Cruise Control, NOR the QL system, does the QL lower ride height when you engage the ACC? I thought the QL lowered the rear ride height to "Aero" mode when you hit a certain highway speed. I can't imagine why they would want to lower ride height when you engaged the ACC? But I don't have either system, so I don't know for sure.....

QL, that lowers and raises the ride height has nothing to do with the brakes....
The ACC, I'm pretty sure can signal the ABS to activate brakes to slow down.... ....so it's only tie to the brakes is the ability to send a message on the CAN Bus to the ABS module to engage the brakes to slow down..... ....it must be able to signal to release the brakes... ...regardless when you hit the brakes the ACC should disengage and not be sending messages....

The Term Electronic Assist, I can't say its incorrect, but it can be confusing.. ....many things on the WK2 are electronically controlled.... ....some of them, like the brakes are not totally electronically controlled, the electronics recognize certain situations and intervene with electronic control, you could call that Electronic Assist....

But the brakes and steering are Power Assisted, a.k.a. Power Boosted....

The brakes are purely hydraulic for normal situations, no different than brakes from the 1950's worked, the one difference, the brake plumbing is run the ABS module and back out again. So for normal situations, the brake pressure goes in and out of the ABS module no different than if there was just a line there instead.....

When a situation occurs that the electronics have to intervene, the various modules for ACC/TC/BTCS/ESP will send messages on the CAN Bus telling the ABS module to open valves and/or activating the pump, to increase or decrease brake pressure at various or all brakes....

So the electronics could cause this, but not likely and even less likely without lighting warning lights on the dash, or giving symptoms of the ABS activating, like pedal pulsating, the dinsticitive "thunk, thunk" noise of the ABS pump.......

I tend to think the most likely culprit might be the trans shifting late or early, causing an engine braking effect that changes to force of braking....
 

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Discussion Starter #12
What I was referring to was shifting into neutral and then slowing down through the same gears and speed (25mph-20mph) and experiencing a smooth stop with no jolting or lunging forward by the car.
Thoughts ?
 

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What I was referring to was shifting into neutral and then slowing down through the same gears and speed (25mph-20mph) and experiencing a smooth stop with no jolting or lunging forward by the car.
Thoughts ?
Yep, by putting it into neutral while recreating the conditions you've removed the transmission from the equation.... ...so its very likely your problem is transmission "related"... ...there might not be anything wrong with the trans but instead electronics, or electronic throttle.....

The Trans downshifting to a lower gear should not make you lunge forward, only if the throttle (which the PCM is controlling) gave it some gas as you downshifted would it lunge forward....

You've confirmed you're not hitting the the accelerator with your foot as you brake?

Repeat this experiment, but this time watch the engine rpm, see if the engine rpm jumps up as you hit that spot you normally lunge forward....
 

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Yep, by putting it into neutral while recreating the conditions you've removed the transmission from the equation.... ...so its very likely your problem is transmission "related"... ...there might not be anything wrong with the trans but instead electronics, or electronic throttle.....

The Trans downshifting to a lower gear should not make you lunge forward, only if the throttle (which the PCM is controlling) gave it some gas as you downshifted would it lunge forward....

You've confirmed you're not hitting the the accelerator with your foot as you brake?

Repeat this experiment, but this time watch the engine rpm, see if the engine rpm jumps up as you hit that spot you normally lunge forward....
TRANSMISSION... my least favorite word when it comes to cars...

I just dropped off the jeep at my jeep dealer out here in San Jose (Normandin Chrysler Jeep Dodge) and they usually do a really good job. The tech I spoke to seemed to think it may be a software issue but indicated its something he hasnt really seen, so that worried me.

But to answer your questions, yes. When slowing down the RPM's jump when going through the 28-25mph range with only my foot on the brake and not on the gas.

I have used my ACC alot on this vehicle and I don't know if that has something to do with it. I guess I will wait and see what they say. They said it will likely stay overnight and I'll grab it tomorrow so ill keep everyone updated on the results.
 

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But to answer your questions, yes. When slowing down the RPM's jump when going through the 28-25mph range with only my foot on the brake and not on the gas.
This was when the vehicle was in neutral as you slowed down.....

Neutral will disconnect the engine from the trans..... ....so the trans doing something could cause the engine rpm to jump up if they are connected, i.e. in gear, if you're in neutral and the engine rpm jump up without touching the gas, then that's the engine doing it itself......

Software Issue? Software doesn't change, but its possible stored corrective factors have some bogus data in them, causing a change that is wrong enough to be a malfunction... ...so they can clear that data, a.k.a. as quick learn mode, Reseting the Module....

If you were in neutral when you witnessed the engine rpm jumping up on its own, it could be a sensor or Electronic Throttle Control issue..... ...keep your fingers crossed it might just be a bad sensor or a bad Electronic Throttle Body and from the dealer that could be rather expensive, but far cheaper than a transmission....
 

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Discussion Starter #16
This was when the vehicle was in neutral as you slowed down.....
No. Only while in DRIVE the RPM's jumped and the car lunges forward....

While in neutral the problem was completely fixed. No jumping through 28mph-20mph. and no RPM jumping
 

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No. Only while in DRIVE the RPM's jumped and the car lunges forward....

While in neutral the problem was completely fixed. No jumping through 28mph-20mph. and no RPM jumping
Yea, when the trans downshifts the engine rpm should jump up..... ....but that would only increase your engine braking and slow you down more, not cause you to lunge forward.....

So its possible the trans or engine is doing this, or somehow miscommunication and both are contributing.....
 

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Discussion Starter #19
Technician found a software update to fix the issue. After updating the software the tech said it shifts much better. Im picking it up shortly to see the difference
 

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Technician found a software update to fix the issue. After updating the software the tech said it shifts much better. Im picking it up shortly to see the difference
Keep your finger crossed, hopefully it works.

Software doesn't wear, it doesn't change with times.... ...it should not work any differently 100k miles down the road than it did coming off the lot at 50 miles.....

But remember the Adaptive Function, the Correction Factors stored in memory that I spoke about earlier.... ....this is the software adapting for wear or conditions... ...and there have been cases where certain conditions causes bogus corrective data to be stored in memory, and that causes less than perfect reaction or bad reactions by the transmission or whatever equipment that is being controlled....

So, there could be improved software that corrects the storage of these corrective factors and prevents bogus data that cause malfunctions like you were encountering....

So again, keep your fingers crossed, hopefully a software update actually does fix this....
 
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