Which parts fail
Components named in complaints (accelerator pedal, throttle, sudden acceleration, cruise control).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2015 Kia Optima owners, lightly cleaned up (personal details are redacted by NHTSA).
3 months prior to my car going into limp mode I had an incident where I was on the highway and had to come to a stop of major traffic and suddenly my car cut off out of nowhere. I got it to crank after putting it in park, but it was very scary being on the highway thank God it was traffic to where cars wasn't going so fast. Fast-forward to my recent incident to now my car's now in limp mode (MIL) same situation different times was getting on the highway and started to pick up speed to accelerate to 60mph my engine light started to blink Non-Stop and here I am again in a terrifying situation to where I have to get back off of the freeway and I also was on my way to work now having to call in and praying and hoping nothing happens to me while trying to get my car home now I've called I'm certain dealerships decided to go with a dealership to get my recalls done and the dealer basically …
The contact owns a 2015 Kia Optima. The contact stated that while driving at a slow speed while at a fuel station, the vehicle suddenly experienced unintended acceleration while the brake pedal was being pressed. During the failure, the RPM's suddenly increased although the accelerator pedal was not being depressed. The vehicle was turned off and restarted four times before the vehicle operated as normal. On a second occasion, the failure had reoccurred while driving approximately 35 MPH while slowing to approach a stoplight. The vehicle was taken to the local dealer, but no information was available. The manufacturer was not yet notified. The failure mileage was 46,900
The contact owns a 2015 Kia Optima. The contact stated while driving at an undisclosed speed, the accelerator pedal was depressed; however, the vehicle failed to accelerate as intended. Additionally, the steering seized. The contact stated that the steering wheel was difficult to turn, and the vehicle lost motive power. The vehicle was restarted; however, the failure reoccurred. The vehicle was towed to the residence. The vehicle was not diagnosed or repaired by an independent mechanic or the dealer. The manufacturer was made aware of the failure. The failure mileage was approximately 174,000.
The contact owns a 2015 Kia Optima. The contact stated that while driving at an undetermined speed, the vehicle failed to accelerate and stalled. There were no warning lights illuminated. The vehicle was towed to the local dealer where it was diagnosed that an engine replacement was needed. The vehicle was not repaired. The manufacturer was notified and informed him that he had failed to complete the knock sensor detection system (KSDS) repair and provided no additional assistance. The failure mileage was approximately 106,000.
The contact owns a 2015 Kia Optima. The contact stated that while driving approximately 70 MPH, the vehicle inadvertently decelerated to 60 MPH. The vehicle began to shudder and failed to accelerate above 20 MPH. The check engine warning light was illuminated and flashing. The local dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not contacted. The approximate failure mileage was 80,000.
The contact owns a 2015 Kia Optima. The contact stated while driving uphill at 20 MPH, the vehicle hesitated and the accelerator pedal was depressed; however, the vehicle stalled. The contact stated that the check engine warning light was illuminated. The local dealer was contacted. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure. The approximate failure mileage was 120,000.
I was driving in downtown Gilbert when I pulled up to a red light. My car would not inch forward when taking foot off brake. I then had to put my foot all the way down to get my car to drive. When taking a turn my car would run perfectly until I stopped. Then we pull up to parking garage and the car just stops without while in drive so I put it in park and then turn it off and then back on and it works again. I had the alternator, battery and starter checked and they were all good no issues so why am I having electrical problems with my vehicle Kia needs to fix this.
The engine lost power taking off crossing a major roadway, resulting in a stall, vehicle had to be restarted in a panic. The knocking and loss of power put me and my passenger in danger of a side impact from cross traffic. The issue was reproduced by a dealer upon further inspection. The vehicle will be inspected by a service department at certified dealership. No warnings lights or fault warnings appeared related to this issue.
When driving on the highway my car suddenly started to stall with me on the highway. It went from 80 miles per hour to 20 miles per hour and then completely shut off in the lane of the highway. Thankfully I was able to pull over to safety. I attempted to start again, and the engine started with a weird noise coming from it. I had it towed to my local Mechanic who told me that my engine is part of a safety recall.
I was on the freeway and out of no where I couldn't accelerate and immediately my car slowed down and I had to get over the car behind me had to slam on breaks and I was almost hit twice car then flashed to pull over and charge battery but it's a brand new battery everything still turned on just couldn't accelerate so it's now towed to Kia dealership to get diagnostics done scariest driving moment ever
NHTSA investigations
Throttle control system vulnerabilities
The Office of Defects Investigation (ODI) of the National Highway Traffic Safety Administration (NHTSA) received a petition letter dated October 10, 2021, requesting an investigation of possible defects in the electronic throttle control (ETC) system on certain Kia vehicles resulting in the opening of DP21-003.
Acceleration complaints in other Optima years
Frequently asked questions
How common are acceleration problems on the 2015 Kia Optima?
NHTSA has 36 complaints about the speed control & acceleration of the 2015 Kia Optima, 4% of the model year's 1,009 complaints. The component named most often is accelerator pedal (2 mentions).
Is there a recall for 2015 Kia Optima acceleration problems?
No. NHTSA lists no speed control & acceleration recall for the 2015 Kia Optima, though it has 4 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2015 Kia Optima acceleration problems start?
Half of the complaints with a recorded mileage happened before about 61,000 miles, and 10% before 25,000 miles.
Is it dangerous?
Owners linked 3 crashes, 0 fires and 2 injuries to speed control & acceleration problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.