Seeking advice on brake vibration and engine 'jumps' at higher speeds after fixing ignition coil issue

[taamaas]

Hi all,

After fixing the ignition coil issue, I have noticed two other issues with my car that I am hoping to find a solution for.

Firstly, I have experienced vibration when braking at higher speeds. Although I haven't noticed it at lower speeds, after some spirited driving and braking, I can feel the car and steering wheel vibrating when stepping on the brake pad. I am wondering if I should change the rotors, pads, or maybe both? I would appreciate any recommendations or advice.

Secondly, I have noticed that at higher speeds, when I step on the gas, the car accelerates well, but I sense minor "jumps" as the RPM increases, as though the engine couldn't handle the acceleration. I am not flooring it and the slight "jumping" goes away when I let off the gas a bit, and the Stinger continues to pick up speed. I didn't notice this during heavy accelerations at lower speeds (lower gears). I changed the ignition coil when I got the cylinder 6 misfire code, and it seemed to solve the misfire issue. However, I am wondering if I should change the spark plug for that cylinder as well.

Any ideas or recommendations would be greatly appreciated! Thank you.

 

[Snicklefritz]

you probably have another coil pack / plug acting up. backing off of boost makes the 'jumps' go away. when my no. 6 coil pack failed the only time I noticed anything wrong was when I accelerated enough to engage the turbos. the car felt entirely normal otherwise. the cel only came on under boost.

 

[bfglitch]

As for the brakes...here ya go FAQ: Vibration under braking: warped rotors? NO!

Lots of recommendations. Pretty much all say to swap to aftermarket pads and possibly either replace rotors, or have them resurfaced. Some have been able to get away with just swapping pads.

 

[Snicklefritz]

As for the brakes...here ya go FAQ: Vibration under braking: warped rotors? NO!

Lots of recommendations. Pretty much all say to swap to aftermarket pads and possibly either replace rotors, or have them resurfaced. Some have been able to get away with just swapping pads.

And some have first done a fierce bedding in of the oem rotors successfully, which means that braking was smoothed out. then they got aftermarket pads on right after that and that worked for them. the oem rotors are good ones.

 

[bfglitch]

And some have first done a fierce bedding in of the oem rotors successfully, which means that braking was smoothed out. then they got aftermarket pads on right after that and that worked for them. the oem rotors are good ones.

Yeah forgot to mention that one which is odd considering that's exactly what I did and no longer have the issue.

 

[taamaas]

you probably have another coil pack / plug acting up. backing off of boost makes the 'jumps' go away. when my no. 6 coil pack failed the only time I noticed anything wrong was when I accelerated enough to engage the turbos. the car felt entirely normal otherwise. the cel only came on under boost.

Yes, that's exactly what I'm experiencing. Should I take it to the dealership and have them diagnose/change all coils and plugs? I paid out of pocket for the cylinder 6 coil, and after installing it, the car was fine even under boost for the past few weeks. However, yesterday, while driving on the highway and after stepping on the gas moderately but firmly, the CEL suddenly came on. I took the closest exit, stopped at a gas station, and could feel the same vibration as before - a cylinder misfire. After turning off and back on the car, everything was gone, no CEL, no vibration. I tried to replicate the issue while heading to an AutoZone to have it diagnosed (because I'm curious if the misfire came from the same cylinder again or if it was another one) but of course it didn't do that again. Given the situation, should I take it back to the dealership or try to find an independent mechanic who is experienced with Kia/Stingers?

 

[taamaas]

As for the brakes...here ya go

Lots of recommendations. Pretty much all say to swap to aftermarket pads and possibly either replace rotors, or have them resurfaced. Some have been able to get away with just swapping pads.

Thanks, I will most likely switch the pads myself, I'm just trying to find which ones to get.

Also, do you think this break issue would be covered under warranty?

 

[Snicklefritz]

Yes, that's exactly what I'm experiencing. Should I take it to the dealership and have them diagnose/change all coils and plugs? I paid out of pocket for the cylinder 6 coil, and after installing it, the car was fine even under boost for the past few weeks. However, yesterday, while driving on the highway and after stepping on the gas moderately but firmly, the CEL suddenly came on. I took the closest exit, stopped at a gas station, and could feel the same vibration as before - a cylinder misfire. After turning off and back on the car, everything was gone, no CEL, no vibration. I tried to replicate the issue while heading to an AutoZone to have it diagnosed (because I'm curious if the misfire came from the same cylinder again or if it was another one) but of course it didn't do that again. Given the situation, should I take it back to the dealership or try to find an independent mechanic who is experienced with Kia/Stingers?

dealership while under warranty, which is 60,000 miles on electrical. the older stinger has over 60,000 miles and any coil pack or plug that goes bad will only be covered if the item in question failed within the warranty period of the part. a bad coil can quickly ruin a plug and the plug should be under warranty for the part even if the car has more than 60,000 miles. at this point if any other coil failure happens it is on me. if you have a good mechanic that charges less than the dealership then the answer is obvious.

 

[rpoffen]

Yes, that's exactly what I'm experiencing. Should I take it to the dealership and have them diagnose/change all coils and plugs? I paid out of pocket for the cylinder 6 coil, and after installing it, the car was fine even under boost for the past few weeks. However, yesterday, while driving on the highway and after stepping on the gas moderately but firmly, the CEL suddenly came on. I took the closest exit, stopped at a gas station, and could feel the same vibration as before - a cylinder misfire. After turning off and back on the car, everything was gone, no CEL, no vibration. I tried to replicate the issue while heading to an AutoZone to have it diagnosed (because I'm curious if the misfire came from the same cylinder again or if it was another one) but of course it didn't do that again. Given the situation, should I take it back to the dealership or try to find an independent mechanic who is experienced with Kia/Stingers?

You need to scan to get the code when this happens. It might actually have been an overboost going into limp mode which can feel like a misfire. It will clear up on restart, until the next time.
What year is your Stinger and what mods? The 2022+ models have been more prone to this, some even stock!

 

[taamaas]

You need to scan to get the code when this happens. It might actually have been an overboost going into limp mode which can feel like a misfire. It will clear up on restart, until the next time.
What year is your Stinger and what mods? The 2022+ models have been more prone to this, some even stock!

I have a 2020 GT2 AWD with BMS cold air intakes. That's the only thing I could see when I bought the car with 23k miles. However, I found a small red cylinder like thing with a pin on one side that resembles to the plug part of the JB4 so I'm pretty sure that was installed too before someone decided to sell the car and take out the tune. To be honest with you, I'm not even sure what else was done to the car. I wish I did more research before buying but I still hope this is an issue that can be fixed relatively easily and won't cost a whole lot. I purchased 6 HKS plugs that I'm planning on installing this weekend and hopefully that will give it a fresh start.

The code I got the second time this issue happened (that's when the CEL stayed on even after restart) was P0306, cylinder 6 misfire. I experienced the same issue (acceleration, CEL, vibration at low speed) two days ago and although I wasn't able to have it diagnosed, I'm pretty sure it was a misfire again as I could feel the vibration...

Do you think the car would vibrate slightly when going into limp mode because of an overboost? What's a fix for that?

 

[rpoffen]

I have a 2020 GT2 AWD with BMS cold air intakes. That's the only thing I could see when I bought the car with 23k miles. However, I found a small red cylinder like thing with a pin on one side that resembles to the plug part of the JB4 so I'm pretty sure that was installed too before someone decided to sell the car and take out the tune. To be honest with you, I'm not even sure what else was done to the car. I wish I did more research before buying but I still hope this is an issue that can be fixed relatively easily and won't cost a whole lot. I purchased 6 HKS plugs that I'm planning on installing this weekend and hopefully that will give it a fresh start.

The code I got the second time this issue happened (that's when the CEL stayed on even after restart) was P0306, cylinder 6 misfire. I experienced the same issue (acceleration, CEL, vibration at low speed) two days ago and although I wasn't able to have it diagnosed, I'm pretty sure it was a misfire again as I could feel the vibration...

Do you think the car would vibrate slightly when going into limp mode because of an overboost? What's a fix for that?

I have had an overboost happen once or twice (I am tuned with a bunch of stuff you can see in my sig), and when it happens, the engine runs rough and weird stuff. Clears when I restart.
If you are getting a misfire code, then that's not overboost. There is a thread on this forum where someone was chasing misfire codes and turned out that a bad coil was making plugs go bad and vice-versa. He had to change both coil and plug at the same time.

 

[taamaas]

I have had an overboost happen once or twice (I am tuned with a bunch of stuff you can see in my sig), and when it happens, the engine runs rough and weird stuff. Clears when I restart.
If you are getting a misfire code, then that's not overboost. There is a thread on this forum where someone was chasing misfire codes and turned out that a bad coil was making plugs go bad and vice-versa. He had to change both coil and plug at the same time.

Got it! Thanks for your help!

On a Facebook Stinger group, someone mentioned that a bad plug could blow the coil as well. Knowing that I just changed the coil on cylinder 6 (without replacing the plug), please tell me that it didn't blow a brand new coil. I'm hoping if I replace all plugs I currently have with brand new HKS plugs, the problem will go away. Any idea what gap should I use knowing that the car is not tuned (besides COI)?

 

[rpoffen]

Got it! Thanks for your help!

On a Facebook Stinger group, someone mentioned that a bad plug could blow the coil as well. Knowing that I just changed the coil on cylinder 6 (without replacing the plug), please tell me that it didn't blow a brand new coil. I'm hoping if I replace all plugs I currently have with brand new HKS plugs, the problem will go away. Any idea what gap should I use knowing that the car is not tuned (besides COI)?

I also troll the stringer owners facebook group, so maybe it was me.
For a stock setup, I would go with HKS plugs at .024. This would also work if you have a jb4.
For gapping plugs, use a real gap tool something like this.

https://www.amazon.com/gp/product/B0B25LGSSG

 

[taamaas]

I also troll the stringer owners facebook group, so maybe it was me.
For a stock setup, I would go with HKS plugs at .024. This would also work if you have a jb4.
For gapping plugs, use a real gap tool something like this.

https://www.amazon.com/gp/product/B0B25LGSSG

Well, if that was you, you got me!

I have a gapping tool already but I appreciate the advice. In addition to the plug changes, I'll replace the brake pads (with K8SS Elite Sport Ceramic Brake Pads) and also replace the BMS filters on the CAI. Hopefully with doing all this, both the brake vibration and misfire issue will go away.

I appreciate all the help you guys provide!!

 

[Silverfox]

Thanks, I will most likely switch the pads myself, I'm just trying to find which ones to get.

Also, do you think this break issue would be covered under warranty?

My vibrating brake issue was covered under Warranty. Pads and discs were replaced but it returned after a couple of thousand miles.

 

[rpoffen]

My vibrating brake issue was covered under Warranty. Pads and discs were replaced but it returned after a couple of thousand miles.

OEM pads are to blame. Put good aftermarket pads on and bed them well.