Acceleration while slowing...

[Kevin_D]

Today I was coming down a fairly steep dirt road, and I had the AT in manual, first gear, rather than ride the brakes.
I noticed that the motor would accelerate at intervals, rather than just staying at an idle to slow me down.
Has anyone else experienced this, or do I need to seek service?

Kevin

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[Blade1668]

I've had the same thing happen, with it just driving around and as it coasting down a hill. Down shifting then RPM jump up. Is that what you're talking about?

 

[Kevin_D]

As I was coasting down the hill in 1st gear, it acted like the throttle was blipped; I didn’t look at the tach, but the fuel economy went from 99 to ~50, and I could feel the push. It was brief, but noticeable, and happened repeatedly.

Kevin

 

[BigRed97]

Mostly like due to the converter locking and unlocking to control speed. With it unlocked the engine will be at idle and when it locks(or partially locks, not sure if it's a own system) rpm go up.

 

[DAVECS1]

My strong opinion is, this is due to the air flow model for the electronic throttle. I have been tunning this a great deal lately. I am not sure how it was done in the past, bit the tuning on this from FCA is not ideal putting it kindly. It has not been tested sufficiently for corner cases and adaptive modes. A pedal commander or product like this may help. The ecm update from Jeep may help. I can make it better with tunning but that is a pricey route to go as an HP tuner unlock and licenses is pushing about 500 I think. If you ise it more it may adapt and do better also I would keep the stock airbox and exhaust on it.

 

[JeepCares]

As I was coasting down the hill in 1st gear, it acted like the throttle was blipped; I didn’t look at the tach, but the fuel economy went from 99 to ~50, and I could feel the push. It was brief, but noticeable, and happened repeatedly.

Kevin

Hey, Kevin. Is this concern still present? Send us a PM with more details if it is so we can assist.

Kate
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[ClunkyJeep]

When I am braking I often feel a surge at some point as the transmission is downshifting. The tac doesn’t rev or anything. I think I am getting some engine braking and then for some reason the transmission will shift to neutral for a moment. Since my brake pressure is based on what I am feeling with the engine braking when it hangs it neutral it feels like it is accelerating when really I need to brake a little more. This has happened a couple of times in traffic and I have come too close to the vehicle in front of me.

 

[JohnFinx]

I have also had this happen when it downshifts to 4th gear, sometimes it will "lunge" ahead as if I hit the gas. This usually happens if I brake a little hard, then let up just as it drops into 4th.

 

[CerOf]

I bet the first gear is probably torque converter locking/unlocking.

is the down shift from a higher gear the transmission rev matching?

 

[JeepCares]

When I am braking I often feel a surge at some point as the transmission is downshifting. The tac doesn’t rev or anything. I think I am getting some engine braking and then for some reason the transmission will shift to neutral for a moment. Since my brake pressure is based on what I am feeling with the engine braking when it hangs it neutral it feels like it is accelerating when really I need to brake a little more. This has happened a couple of times in traffic and I have come too close to the vehicle in front of me.

I have also had this happen when it downshifts to 4th gear, sometimes it will "lunge" ahead as if I hit the gas. This usually happens if I brake a little hard, then let up just as it drops into 4th.

Hello, ClunkyJeep and JohnFinx.

Are these concerns still present for you both? We do suggest visiting the dealer for a formal diagnosis but if you need any further assistance, send us a PM.

Kate
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[JohnFinx]

Hello, ClunkyJeep and JohnFinx.

Are these concerns still present for you both? We do suggest visiting the dealer for a formal diagnosis but if you need any further assistance, send us a PM.

Kate
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Yes, it happened today actually. I'm waiting until covid dies down a little before I take it in. I'm in Florida, and the general public here is not safe to be around. (I know the dealership tries, but the customers don't...)

 

[JeepCares]

Yes, it happened today actually. I'm waiting until covid dies down a little before I take it in. I'm in Florida, and the general public here is not safe to be around. (I know the dealership tries, but the customers don't...)

Completely understand, JohnFinx! Whenever you're ready, let us know! Our team is happy to help.

Kate
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[ClunkyJeep]

I have been to the dealership and they can’t seem to duplicate the issue.

Jeep is trying to get this transmission/engine combo to do too much. Need to be able to toggle from tow mode to regular mode so the programming doesn’t need to try and figure out what the hell you want to do.

 

[DAVECS1]

I have been to the dealership and they can’t seem to duplicate the issue.

Jeep is trying to get this transmission/engine combo to do too much. Need to be able to toggle from tow mode to regular mode so the programming doesn’t need to try and figure out what the hell you want to do.

You are absolutely correct

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