Break suddenly applies hard when decelerating

[Pyrotik]

Well, I build engines, I build transmissions, I build rear ends and complete suspensions rebuilds, I've done transmission swaps and custom supercharger installations, and, for kicks, I've done custom interior work and paint.... I'm pretty serious about this hobby.
So IMO it's a pretty damn good guess.
I've felt the same torque converter drag in different cars in different scenarios. Every automatic will do it to one extent or another. It's just pretty pronounced in the kia, especially in the lower gears while coasting. There's literally nothing else it could be unless the brakes are actually applying. And that's wildly unlikely.

Gotcha well thanks for the information I appreciate it and feel better.

 

[Pyrotik]

It's not the brakes, it's the transmission downshifting. If you let off the brakes it'll still happen on decel. Some cars are more aggressive about it, so I assume it's something quirky about how the ECU adapts shifts since people have reported the problem goes away after disconnecting the battery and resetting everything.

Hey I know this is way later but I’m tired of this and want to try the battery test, so I just disconnect the negative, wait a min, and reconnect to reset the battery and hopefully the system?

 

[Blingen]

Hey I know this is way later but I’m tired of this and want to try the battery test, so I just disconnect the negative, wait a min, and reconnect to reset the battery and hopefully the system?

Disconnect for 5 minutes. Another thing you can do is drive in an empty parking lot, get it up to 20 or 25 mph, shift it into neutral, then apply the brakes to start slowing it down. If you still have the sudden grabbing of the brakes, you have ruled out downshifting.

 

[MadSycko]

Did you try to manually downshift before you coast to a stop? That way, the gear will remains to gear up to full stop before going back to auto drive.. this would eliminate the rough downshift from the equation.

 

[Pyrotik]

Disconnect for 5 minutes. Another thing you can do is drive in an empty parking lot, get it up to 20 or 25 mph, shift it into neutral, then apply the brakes to start slowing it down. If you still have the sudden grabbing of the brakes, you have ruled out downshifting.

If In which case it is the downshifting, then nothing I do will fix that I suppose.

 

[ShannonC]

If In which case it is the downshifting, then nothing I do will fix that I suppose.

A trip to the dealer might bring some satisfaction. Recently a member in Aus had aggressive downshifts from 3rd to 2nd. Dealer tested it and found upshifts in sport were also too aggressive. Transmission was replaced under warranty.

 

[Blingen]

Disconnecting the battery could reboot the ECU and solve it. Also if it is downshifting, you could tell the service manager what you did to narow down the issue. They may need to do an ECU? refresh. Don't give up on the issue. For example my last car had an issue with the heated seat. There was a 1 inch area that got extremely hot. I had someone else drive the car and they said the same thing. The service manager said the car is not throwing any codes and voltage meter showed no issues. It took me another trip and convinced him to turn on the heater and sit in the car for 15 minutes. He came back 20 minutes later and said wow, you have a problem with the seat heater and replaced it under warranty. They showed me the old one and where it had started melting.

 

[Pyrotik]

Disconnecting the battery could reboot the ECU and solve it. Also if it is downshifting, you could tell the service manager what you did to narow down the issue. They may need to do an ECU? refresh. Don't give up on the issue. For example my last car had an issue with the heated seat. There was a 1 inch area that got extremely hot. I had someone else drive the car and they said the same thing. The service manager said the car is not throwing any codes and voltage meter showed no issues. It took me another trip and convinced him to turn on the heater and sit in the car for 15 minutes. He came back 20 minutes later and said wow, you have a problem with the seat heater and replaced it under warranty. They showed me the old one and where it had started melting.

I think I’ll give it a try and go ahead and insulate my air bag while I’m at it since it’s popping like crazy too. Hopefully it refreshes it that would be nice.
I have an appointment November 12th for them to look at it.

 

[Pyrotik]

Oh by the way, it rolls to a stop even while breaking beautifully when in neutral. So it’s definitely aggressively downshifting.

weird thing is it doesn’t always happen, like 95% of the time it does but sometimes it won’t, seems more like when engine is nice and warm it won’t do it, WEIRD

 

[Blingen]

I think I’ll give it a try and go ahead and insulate my air bag while I’m at it since it’s popping like crazy too. Hopefully it refreshes it that would be nice.
I have an appointment November 12th for them to look at it.

Take a look at this posting.

The hard downshifts in sport mode

I've noticed this becoming increasingly more lately, if I'm slowing down slowly and applying moderate pressure to the break sometimes the downshifts in sport mode just feel pretty hard and jerky at times, slowing the car down themselves. If I stop alot faster then there is no issue as the...

stingerforum.org

Sounds like your issue with possible solutions.

 

[Pyrotik]

Take a look at this posting.

The hard downshifts in sport mode

I've noticed this becoming increasingly more lately, if I'm slowing down slowly and applying moderate pressure to the break sometimes the downshifts in sport mode just feel pretty hard and jerky at times, slowing the car down themselves. If I stop alot faster then there is no issue as the...

stingerforum.org

Sounds like your issue with possible solutions.

So I read through this whole thing and it sounds like I need to let the dealership do an ECU reset. I wanted to try disconnecting the battery for 20 minutes but holy crap, I can’t figure out how to do it! It’s like the weirdest set up for a battery I’ve ever seen lol I’m kinda afraid to mess with it.

 

[Blingen]

So I read through this whole thing and it sounds like I need to let the dealership do an ECU reset. I wanted to try disconnecting the battery for 20 minutes but holy crap, I can’t figure out how to do it! It’s like the weirdest set up for a battery I’ve ever seen lol I’m kinda afraid to mess with it.

Oh! I got this one.
Here is the steps I follow:
1. Gather tools. I made sure I had 2 adjustable wrenches, my socket sets-standard and metric. Not sure which one it is.
2. Flashlight, headlamp or worklight.
3. Removed everything so I could get to the battery and made sure nothing would fall into the battery compartment.
4. Drape towels over the area so I did not scratch anything.
5. Safety first, safety glasses.
6. I looked at the wiring back there.
7. Pulled out my phone, called 302-527-2700. Pressed Option 2 to set up service at the local Kia dealer.
8. Put everything back the way I found it and drop the car off.

I normally replace step 3 and 6 with whatever I am looking at on the car--I have realized my limitations and hats off to everyone on here that has upgraded their stinger.
Couldn't resist sharing my normal car repair process.

On a serious side, I think you just need to disconnect the ground black wire side from the terminal and let it set for 20 to 30 minutes. I normally wrap the cable end in a towel to make sure it does not spring back and touch the battery post. I don't mess with the positive side unless I need to replace the entire battery. Maybe some of our DIY techs on here will chime in.

 

[MerlintheMad]

So I read through this whole thing and it sounds like I need to let the dealership do an ECU reset. I wanted to try disconnecting the battery for 20 minutes but holy crap, I can’t figure out how to do it! It’s like the weirdest set up for a battery I’ve ever seen lol I’m kinda afraid to mess with it.

In the engineroom, remove that cover in the RR corner and then disconnect the positive cable.

 

[Pyrotik]

Oh! I got this one.
Here is the steps I follow:
1. Gather tools. I made sure I had 2 adjustable wrenches, my socket sets-standard and metric. Not sure which one it is.
2. Flashlight, headlamp or worklight.
3. Removed everything so I could get to the battery and made sure nothing would fall into the battery compartment.
4. Drape towels over the area so I did not scratch anything.
5. Safety first, safety glasses.
6. I looked at the wiring back there.
7. Pulled out my phone, called 302-527-2700. Pressed Option 2 to set up service at the local Kia dealer.
8. Put everything back the way I found it and drop the car off.

I normally replace step 3 and 6 with whatever I am looking at on the car--I have realized my limitations and hats off to everyone on here that has upgraded their stinger.
Couldn't resist sharing my normal car repair process.

On a serious side, I think you just need to disconnect the ground black wire side from the terminal and let it set for 20 to 30 minutes. I normally wrap the cable end in a towel to make sure it does not spring back and touch the battery post. I don't mess with the positive side unless I need to replace the entire battery. Maybe some of our DIY techs on here will chime in.

Lmao thanks I think that’s all I need to do as well just no telling what works when there’s no indications anywhere