2018 Kia Optima Fuel system Problems

I am submitting this complaint regarding ongoing and persistent mechanical issues with my vehicle since the time of purchase. The vehicle has repeatedly shut off unexpectedly, creating a serious safety concern. Initially, I suspected the issue might be related to the battery, and I have replaced the battery twice within the past 4 years. However, the problem has continued. In January, the vehicle began shaking and shutting down again. I took it to a mechanic, who diagnosed the issue as faulty spark plugs and an ignition coil. The diagnostic codes provided were P0303 and P0456, and the recommended repairs were completed. Approximately one month later, the vehicle began shutting off again. I then took it to the dealership, where I was advised that the valve cover gasket needed to be replaced, along with the belts, and that a fuel system cleaning was required. I subsequently had these repairs completed by my mechanic. Less than a week after completing those repairs, the vehicle once again began shutting down. A diagnostic scan then produced code P123300. In addition to these repeated shutdowns, the vehicle consumes an excessive amount of oil, has poor acceleration, and continues to stall unexpectedly both while driving on the road and while idling, such as in a drive thru. These recurring issues have made the vehicle unreliable and unsafe. I am concerned about the risk of the vehicle shutting off while in motion, which could lead to a dangerous situation. I am requesting that this matter be reviewed for potential defects or safety-related concerns.

NHTSA ID

11725280

Incident

Mar 17, 2026

On August 26, 2025, I brought my 2018 Kia Optima Plug-In Hybrid to an authorized dealer for recall SC218 (engine inspection and KSDS software update). The dealer verbally stated both SC218 and SC278 recalls were completed, and the repair order (RO #XXX) lists them as performed. In September 2025, Kia America emailed me showing recall SC218 still open, and a warranty coverage report dated September 26, 2025, again listed SC218 as unclosed. On November 4, 2025, NHTSA’s official VIN lookup confirmed the recall remains “Incomplete.” On October 21, 2025, Kia America emailed me under Case #XXX stating that SC218 was “confirmed completed” and that the dealer performed a software update to the ECU, referencing RO #XXX. However, NHTSA’s database still lists recall SC218 as incomplete. This contradiction between Kia America’s internal record, the dealer’s invoice, and the federal NHTSA database raises a serious safety concern that the recall inspection or software update was never actually performed or was never reported correctly. I have requested written proof and diagnostic data (Battery SOH report) multiple times but have not received them. If accurate, this means I was led to believe my vehicle’s engine-safety recall had been repaired when federal records still list it as open. I am requesting NHTSA to review this reporting discrepancy, ensure Kia America and the dealer produce verifiable proof of completion, and confirm that the federal record is corrected. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11697664

Incident

Aug 26, 2025

My 2018 Kia Optima LX began using excessive oil (>3 quarts/1000 miles) just over 100K miles. I researched and found that the Theta II engine in my car is known for this. When I took my car to dealership (Stokes Hodges Kia, North Augusta, SC), with the check engine light on, they told me me plugs were fouled (they were just replaced 1 yr prior), cylinder 3 misfiring, and that I needed to pay a few thousand dollars to have repaired. When I asked them to guarantee the soaking process they recommended, they responded that they couldn't, that it "only worked 80% of the time." I have the KSDS download since 2019 and asked them to follow the guidelines of their TSB ENG 222 for the class action lawsuit and start a 1000 mile oil consumption test. they refused, basically telling me the only way to get a new engine from Kia, since my car is over 100K miles, is to drive it until the engine seizes. I expressed my fear for personal safety, but they wouldn't help me. I am original owner and have all services, etc documented. I called Kia customer affairs, then was told only local dealership could help. they stuck me in a loop between them without helping. Please help me.

NHTSA ID

11674425

Incident

Jun 25, 2025

Purchased car about 4 months ago, before warranty ran out, the shop looked at it told me it was fine, it wouldn't accelerate. Few weeks later same issue but all my oil was gone, they found 11 things wrong with the vehicle, told me warranty wouldn't take care of it unless the engine blow up. The salesman Scottie Mitchell told me check Kia for recalls, called Kia 3 recalls, they were trying to finance another car higher, back wanted to know why the dealership didn't know about recalls, Kia place did call a Robert. One of the owners did know about recalls, why dealership didn't pass them on. They trying to sell me a higher vehicle to keep cover the cost of the one I got 1st

NHTSA ID

11672508

Incident

Jul 10, 2025

THE FUEL PUMP HAS AN ACTIVE RECALL. TOOK ITIN TO DEALER AND WE ARE BEING ADVISED KIA WILL NOT COVER THE COST. THEY HAVE AN ARTICLE OUT THAT CLEARLY STATES THEY WILL COVER THE COSTS. THE CAR WREAKS OF THE SMELL OF GAS AND WE ARE SCARED IT WILL CATCH FIRE.

NHTSA ID

11553112

Incident

Oct 7, 2023

Leaking gas at the firewall when running.

NHTSA ID

11540760

Incident

Aug 21, 2021

purchased my car in june of 2019. Ive scheduled regular oil changes and maintenance until june of 2020 where the engine light began to flicker and the car would shake. I took to Koons Kia owings mills md and it was repaired. Next year same thing. Oil compression issues all year round where i have to keep putting oil in. Now my car starts and shakes violently. the kia service modurator on the car indicated there were an engine issue. I cannot keep dishing money into this car with so many recalls (current fuel pump recall and anti theft issue) is also included. Please help

NHTSA ID

11539542

Incident

Aug 19, 2023

I'm reporting these issue pertaining to the engine within the first 3 weeks AFTER the engine replacement recall was serviced and completed. The vehicle was exhibiting the same defects and major health and safety hazards as before the new engine. Intermittent engine failure, even worse, while i was trying entering the hwy at speeds of 45-50 miles it jerked very violently and loss total power while vehicles were behind me nearly rear ended. Prior to this I reached out multiple times to have it serviced at again. The original service department didn't respond, so I called other service departments and was told it needed to be serviced by the original dealership/service department that replaced the engine. I had the vehicle in normal working conditions a few days before it began exhibiting the same problems as before the engine replacement. It was in operable condition but still stalling and refusing to crank unless primed, until it ultimately just would not crank at all and is back in the same condition it was before the new engine but it is not locked up currently. The time frame and Milage between first experiencing the issues to now, March 2023-64745 Started shuddering, loss of power while driving, but would crank right back up without issues. Happened a few times, charged up battery thinking is was am electrical issue. April 2023 More frequently the issues occurred, still same severity levels. May 2023 Began happening every time at an idle, whether I was at a fast food in drive through placing an order, or to wash the car. Every time at an idle this would happen, and would take a few times of trying to start the vehicle and after about 5 seconds of cranking it would catch and work. I began placing the vehicle in neutral while at idle and it would assist In the stalling out sometimes. After a few days of this it refused to crank due to the engine locking up. Milage at this time was 68048. Aug 2023-New engine, drove about 2k miles-70207 current

NHTSA ID

11537251

Incident

Aug 3, 2023

High injector fuel pump top engine mount went out at 68000 miles. It caused the vehicle to stall and lose power and basically cut the car off while driving.

NHTSA ID

11525549

Incident

May 16, 2023

Mileage

68,000 mi

-Knock Sensor Detection System - ECU Logic Improvement - I Was driving with my infant son in the backseat. I was going 70 mph when my car started rapidly losing speed. This happened again with just myself after receiving the car from mechanic. There was heavy traffic and I had to swerve to avoid being hit by an 18-wheeler. - I can see on the website where I received the car from, there is a recall for my exact make and model with the same code but they say there is no recall for my specific car. - The check engine light started flashing and Kia Systems starts talking.

NHTSA ID

11524617

Incident

May 26, 2023

Trying to cut off and jerks when stopping vehicle

NHTSA ID

11482644

Incident

Mar 8, 2020

ECM telling fuel pump to put too much gas, causing exhaust into cabin, unnoticed while in car, but hair and cloth reak of exhaust and getting headaches. Reduced mileage by 20+mpg from 30+ to 11mpg. BSD- no lights or codes thrown by 3rd party, but dealer said there was a code on the BSD. BSD was not working and no codes appeared. NO LIGHTS OR CODES FOR FUEL ISSUE OR BSD, but dealer said there is a recall that I cannot find for fuel and said there was a code for BSD, but it didn’t pop up on my husband’s code reader previously.

NHTSA ID

11477875

Incident

Aug 4, 2022

WHEN DRIVING THIS VEHICLE RATTLES AND SHAKES IT HAS A BURNING SMELL/GAS SMELL. IT CUTS OFF WHILE DRIVING. LOOSES OIL.OIL AT LOW LEVEL BEFORE DUE. THIS MAKE AND MODEL IS NO LONGER BEING MANUFACTURED. IT HAS A KNOWN HISTORY OF ENGINE PROBLEMS. WHY WERE CONSUMERS ALLOWED TO BUY THIS CAR. PROBLEMS ARE ACTIVE AND ONGOING. STARTED ABOUT A YEAR OR CLOSE TO A YEAR AFTER PURCHASE. IT IS A LEMON . THE DEALER WANTS TO DIAGNOSE THE ENGINE, BUT THEY ALREADY KNOW THE ENGINE IS NO GOOD.

NHTSA ID

11416530

Incident

Jul 20, 2019