[2Beans]

Our 2023 GT does a funny thing in cruise control. The rpms constantly fluctuate up and down like that annoying driver who pumps his foot constantly. It’s less dramatic than that, the speed stays constant. It is mildly irritating and I have made an appointment to have it checked out. Has anyone else had this problem?

This happens even on empty level highways.

 

[Tree 44]

How much is the fluctuation? It may be that the road has slight variations in slopes that the computer is adjusting the speed for.

 

[Hammerhead]

Sounds normal to me.

 

[2Beans]

How much is the fluctuation? It may be that the road has slight variations in slopes that the computer is adjusting the speed for.

We drove to Arizona from Oregon and had a lot of very flat driving and it performed this way. Thing is, I can hold my foot on the accelerator and maintain consistent speed without rpm fluctuation. I wonder if Kia engineered this to improve mpg. On a road with a wavy grade and cruise on it was surging like crazy. I guess if everyone’s Soul does it I don’t want to pay the dealership to tell me it’s normal.

 

[Hammerhead]

Not very clear. If the vehicle is surging not normal. With the ivt if you are maintaining a steady speed you will notice varying movements of the tach hand. It's because the ivt is[ shifting] to maintain speed.

 

[TosenR]

Our 2023 GT does a funny thing in cruise control. The rpms constantly fluctuate up and down like that annoying driver who pumps his foot constantly. It’s less dramatic than that, the speed stays constant. It is mildly irritating and I have made an appointment to have it checked out. Has anyone else had this problem?

This happens even on empty level highways.

The speed stays constant, but the RPMs fluctuating is irritating because you can feel it (even though the speed is staying constant) or irritating in some other way?

 

[Alma2020]

We drove to Arizona from Oregon and had a lot of very flat driving and it performed this way. Thing is, I can hold my foot on the accelerator and maintain consistent speed without rpm fluctuation. I wonder if Kia engineered this to improve mpg. On a road with a wavy grade and cruise on it was surging like crazy. I guess if everyone’s Soul does it I don’t want to pay the dealership to tell me it’s normal.

This does not sound anything like normal, and does sound like an IVT problem. Here's a simple test, while using cruise on a relatively level highway shift over into manual mode (you'll see an "S" as the virtual gear you are in) and then upshift once, which will reveal the gear you were in when in automatic "D" before. Now observe if the fluctuation is the same or not.

I've noticed that when using cruise the IVT prefers a lower gear --6 or 7-- when it would otherwise be in 8 if not using cruise, at highway speeds. It sounds like yours is undecided between 2 gears and going back and forth. There is no reason why a dealership should charge you to check this out, your powertrain warranty is to 100,000 miles. And I would insist on going along for the test drive in order to "show them" and verify.

 

[2Beans]

The speed stays constant, but the RPMs fluctuating is irritating because you can feel it (even though the speed is staying constant) or irritating in some other way?

Yes, you Can feel it and hear it and it is quite consistent and perhaps rhythmic. The variation is about up 3 rpm’s down 3 rpm’s. Some variation, and this is all on flat ground.

 

[2Beans]

This does not sound anything like normal, and does sound like an IVT problem. Here's a simple test, while using cruise on a relatively level highway shift over into manual mode (you'll see an "S" as the virtual gear you are in) and then upshift once, which will reveal the gear you were in when in automatic "D" before. Now observe if the fluctuation is the same or not.

I've noticed that when using cruise the IVT prefers a lower gear --6 or 7-- when it would otherwise be in 8 if not using cruise, at highway speeds. It sounds like yours is undecided between 2 gears and going back and forth. There is no reason why a dealership should charge you to check this out, your powertrain warranty is to 100,000 miles. And I would insist on going along for the test drive in order to "show them" and verify.

Oh thank you that does sound like a logical explanation to it’s behavior. We have not played with the manual mode much and will check that out.

 

[Flatsole]

+/- 3 rpm?

 

[Hammerhead]

+/- 3 rpm?

How do you even notice a change that small? If they meant 3k difference now that would be a problem.

 

[Alma2020]

Oh thank you that does sound like a logical explanation to it’s behavior. We have not played with the manual mode much and will check that out.

I have a knack for figuring all sorts of things out, and with the Soul, between many settings offered that few people discover, the tricks of manual mode (other cars will kick you out of cruise if you switch to manual mode, but not Kia) and more. For example, if you like to sometimes has the auto-engine kill feature work, but not every time you stop, if you effectively downshift (1 gear) by going into manual mode while slowing down for a stop, it will disable the auto engine kill during that stop.
Having used cruise extensively for 3 years now with 2 Souls, there should be no instability of RPM and the dealer must address this on warranty. You shouldn't have to use a work-around to fix it, and yes, I am curious if it ceases to occur in manual mode!

 

[Flatsole]

Cruise control doesn't even try to maintain a constant engine speed. A device that controls engine speed is called a governor. And if you had a constant speed governor on your engine, your road speed would fluctuate greatly.

Cruise control maintains a constant road speed (actually wheel speed.) It varies the throttle and thus engine rpm to accomplish that.

 

[Alma2020]

Cruise control doesn't even try to maintain a constant engine speed. A device that controls engine speed is called a governor. And if you had a constant speed governor on your engine, your road speed would fluctuate greatly.

Cruise control maintains a constant road speed (actually wheel speed.) It varies the throttle and thus engine rpm to accomplish that.

Sounds like common knowledge to me, though not related to the conversation.

 

[Flatsole]

Sounds like common knowledge to me, though not related to the conversation.

Dude says his engine speed varies +/- 3 rpm with cruise control engaged and thinks it is indicative of a problem.

 

[2Beans]

Not very clear. If the vehicle is surging not normal. With the ivt if you are maintaining a steady speed you will notice varying movements of the tach hand. It's because the ivt is[ shifting] to maintain speed.

It’s kind of like a sewing machine, constant, not fluctuating with the terrain.

 

[Alma2020]

Dude says his engine speed varies +/- 3 rpm with cruise control engaged and thinks it is indicative of a problem.

If you read the detail, he is on level ground at a constant speed, which is why this is definitely not OK.

 

[TosenR]

It’s kind of like a sewing machine, constant, not fluctuating with the terrain.

Can you video it? Maybe show the tach rhythmically bouncing up & down?

 

[Hammerhead]

Talk about beating a dead horse. What is op accomplishing on here by repeating the same thing over and over? Take the thing to the dealer and let them look at it.
Today my tach went over 5000 rpm, course I had my size 10 right foot to the floor.

 

[rhysoul]

I don’t think any road is completely level and how do you measure +/- 3 rpms?

A dealer is most likely going to tell you it’s normal. I’m only used to cable operated cruise control, not the electronic kind like in your Soul so maybe it’s more sensitive but it seems normal to me.

Unless Alma2020 is on to something with it being an IVT (CVT) problem, I don’t know.