2018 Hyundai Santa Fe Sport: misfire or rough idle

Filed Jul 17, 2026 · Engine · TN

The Hyundai Theta engine is a bad design that has many recalls, a history of oil consumptions, and breakdowns that leave consumers in danger, on the roadside, and out of money. This engine has a design that causes worn engine components and high oil consumption causing reduced engine power, ruined spark plugs, and engine damage with no recourse as a owner. Recently, my family member had a hesitation that causes the car to run rough and display a check engine light. She was in traffic and the vehicle was stopping. Had this been on the interstate it could have been deadly. This IS NOT UNCOMMON for these vehicles. A quick Google search is nationwide proof of an issue with these vehicles and engines that the government needs to hold Hyundai accountable. This particular vehicle has been assessed by a Hyundai and confirmed it is consuming oil at a higher rate than normal, as many other owners have documented. With this most recent issue of stalling out, the mechanic indicated that excessive oil consumption entering the spark plug port has fouled the spark plugs as the design of the engine is flawed. The oil consumption was discovered at approximately 99,000 miles and several steps were completed to "fix" and confirm the issue. There is no "real fix" to the issue due to the inherent design of the motor. Again, this is not a new issue with these cars and there should be recourse that holds Hyundai accountable for bad and dangerous engines. The check engine light did come on as the vehicle began to stall and run rough in traffic.

Filed May 25, 2026 · Engine, Fuel system · KY

2018 Hyundai Santa Fe Sport. Purchased January 2026 took to Oxmoor Hyundai Service Center March 2026. February 2026 began using oil at a measured rate of 700 miles per tank of oil. Used 3 full tanks of oil within the month of February. Oil lights and engine lights on and off and flashing during this time. March 8, 2026, engine light flashed and then stayed on continuously. Engine shook and stuttered and made a loud noise. Engine stalled while I was driving at 35-40 miles per hour. I was able to continue driving to my home with the stuttering and stalling. The next morning I drove it to the Oxmoor Hyundai Service Center. I told relayed the timeline of all symptoms I had experienced over the 2 month lifetime of my ownership. They did not attempt to reproduce the issue. They only entered "shakes in reverse" as the customer provided issue on the intake information. Service Center performed diagnostic, found cylinder misfires on cylinder 2 and cylinder 4. Replaced spark plugs to resolve Cylinder 2. Cylinder 4 continued to misfire. Used Borescope and found broken valve. They did not address the scoring on the cylinder of the valve. Recommended engine replacement. Advised it would not be covered under a warranty because the rod did not break. The oil consumption was proven with documentation from multiple Valvoline visits and the vertical scoring was present on the cylinder with the broken valve in the borescope photo. The Service Center refused to do a Boring Clearance Test or any other test that would prove the engine should be covered under an extended warranty or class action settlement. It wasn't until I reviewed HMA documents uploaded to the BBB Arbitration, that I realized that the information I initially gave to the Service Center of all the symptoms with timelines had not been entered into the system for diagnostic review by Techline. Arbitrator denied my claim under the theta settlement because the rod had not broken yet, BUT she said my engine was defective.

Filed Apr 7, 2026 · Engine, Fuel system · TX

My 2018 Hyundai Santa Fe Sport equipped with a Theta II GDI engine began exhibiting excessive oil consumption, engine knocking, and cylinder misfires consistent with the known Theta II engine defect covered under the Hyundai class action settlement. Prior to the failure, the check engine light illuminated and I experienced repeated misfires and audible engine knocking. The vehicle required frequent oil additions between oil changes due to excessive consumption. The vehicle was taken to an authorized Hyundai dealership where a diagnosis confirmed a burnt valve inside the cylinder head. The dealership recommends replacement of the cylinder head or complete engine replacement to correct the issue. The dealership performed a bearing failure test and attributed the burnt valve to carbon buildup. However, excessive oil consumption in a GDI engine directly accelerates carbon buildup on intake valves, as burning oil deposits carbon on valve surfaces preventing proper seating and causing overheating and valve failure. The carbon buildup is therefore a consequential result of the Theta II oil consumption defect, not an independent cause. The safety risk is significant as engine misfires and knocking while driving create unpredictable loss of power and potential for stalling in traffic. The vehicle is currently not reliably operable. The manufacturer has been contacted regarding coverage under the Theta II settlement. The component is available for inspection upon request at the servicing dealership

Filed Apr 1, 2026 · Brakes, Electrical · KY

I was told by a mechanic that something electrical is wrong with the vehicle it causes the engine to misfire. Different issue than before.

Filed Mar 19, 2026 · Engine · IN

I drove 2.5 hours north to a Marine brother's father's funeral, who unexpectedly passed. I started my drive home and made it to Yorktown in about 15 minutes, and the engine light came on, started flashing, and went into limp mode. I pulled over on I-69 to shut it off, pulled the dipstick, and the oil level was full. I pushed the Bluelink button on my rearview mirror, and HMA sent a tow truck to tow the vehicle to a local dealership about 10-12 minutes away. The dealership did not inspect the vehicle until the following Monday, since it was Friday, three weeks ago. The dealership found DTC codes for misfires in cylinders 1 and 2, multiple-cylinder misfire, and too-high pressure in all four cylinders. The vehicle has had the knock sensor replaced, a KSDS ECM update, and a series of gaskets replaced. It has been burning oil since 69,362 miles and is now not operational, 2.5 hours from home. HMA has declined to replace the engine on a vehicle involved in a class action settlement due to problems with several completed replacements. The dealership has followed the manufacturer's process, and, due to the engine not producing a code it had at 87,986, but now not capable due to piston damage, cylinder scouring, and spark plug damage, the manufacturer has declined a goodwill replacement. The engine failure did put others in harm's way, as it did me when having to pull off the busy interstate to inspect the obvious failure. I have been driving a rental since this situation occurred, have a vehicle that is not operational, and a manufacturer that is not assuming responsibility for the catastrophic failure. I have read numerous forums across several platforms about the Theta 2 engines. The vehicle has been serviced as needed, including multiple requests to fix or repair the engine noises it produced, when the oil level became low, and oil had to be added.

Filed Mar 18, 2026 · Engine · FL

I am reporting a serious safety concern involving a 2018 Hyundai Santa Fe Sport with approximately 132K miles. While driving at highway speed, the vehicle suddenly lost power/velocity and the engine light flashed. This created an immediate safety hazard, as maintaining speed is critical in highway traffic. Within seconds, the vehicle regained power and the warning light turned off, giving the impression that the issue had resolved. Shortly afterward, while exiting the highway, the vehicle began shaking and felt as though it would stall but was able to drive home less than one mile. A mechanic retrieved misfire codes for cylinders 2 and 4. Further inspection revealed internal engine damage in cylinder 4 requiring major rebuild. A full deconstruction revealed that one of the valves in cylinder 4 had partially broken. This failure occurred with little to no warning and involved a sudden loss of power at highway speed, which could have resulted in a serious accident. The vehicle’s warning systems did not provide adequate or persistent alerts prior to significant engine failure. Over the last 6 months it began consuming oil frequently requiring weekly checks, however no warning systems or errors to indicate an underlining concern. Based on research, similar Hyundai vehicles have documented issues involving excessive oil consumption and internal engine damage without sufficient warning. This raises concerns about a potential safety defect affecting engine performance and failure detection.

Filed Feb 20, 2026 · Engine · 120,000 miles · NV

The contact owns a 2018 Hyundai Santa Fe Sport. The contact received an undisclosed recall notification, and the local dealer was contacted; however, there were no appointments available. On a separate occasion, while driving at an undisclosed speed, the vehicle jerked, and the check engine warning light illuminated. The vehicle was taken to an O'Reilly's Auto Parts to be diagnosed, and DTC: P1326 was retrieved. The vehicle was taken to the dealer and the contact was informed that there were damages to the engine caused by engine misfire. The dealer was in the process of determining if the engine needed to be replaced. The contact waited and then called the dealer and was informed that DTC: P1326 was not the correct code and that there was another fault code related to the recall. The contact was informed that the repair would be an out-of-pocket expense. The vehicle remained at the dealer unrepaired. The manufacturer was not notified of the failure. The failure mileage was approximately 120,000.

Filed Nov 3, 2025 · Engine, Fuel system · OH

This engine is burning oil. Its mixing oil with gasoline in the cylinders. Its fouling spark plugs and consuming large amounts of oil with absolutely no visible oil leaks. The exhaust is black. PCV valve is clean. Engine is misfiring due to spark plug fouling. New spark plugs and coils. Multiple dealers have stated this is a KNOWN defect with this particular GDI engine but Hyundai refuses to issue a recall.

Filed May 16, 2025 · Engine · 105,000 miles · MO

The contact owns a 2018 Hyundai Santa Fe Sport. The contact stated that the vehicle experienced excessive oil consumption, causing the engine oil level to be low, with a misfire coming from the engine. The cause of the oil consumption failure was not yet determined, and the vehicle was not repaired. The manufacturer and local dealer were notified of the failure, but no assistance was provided. The failure mileage was 105,000.

Filed May 6, 2025 · Engine · CA

I’ve got a 2018 Hyundai Santa Fe Sport with a Theta II engine that’s failing—burning oil way too fast, coolant mixing in the cylinders, and throwing a P0304 misfire code. It’s been undrivable since late April 2025, and I’m worried about safety because the misfire and engine failure risk could cause it to stall on the highway, putting me and others in danger. It shakes when I try to drive, which feels unsafe. A Hyundai dealer confirmed the issue, finding coolant in the cylinders and the misfire, with no visible oil leak. Oil change receipts show the oil disappearing over a few weeks. The manufacturer reviewed my case but denied the warranty claim, saying it’s not covered since I’m a second owner and it’s not a rod bearing issue, even though the 2021 Theta II settlement should apply to this. The seller didn’t disclose the engine’s defect history when I bought it in 2023. The check engine light came on in early April 2025 with the misfire code, and I noticed the oil issue then. It’ll be out of service over 30 days by mid May 2025, so I’m taking legal action.

Filed Jan 22, 2025 · Engine · 120,700 miles · FL

The contact owns a 2018 Hyundai Santa Fe Sport. The contact stated while driving 65 MPH and depressing the accelerator pedal, the vehicle failed to respond as needed. The contact pulled over to the side of the road. The contact stated that the vehicle was towed to a dealer by a friend. The vehicle was diagnosed with a misfire in the engine. The contact was informed that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure but offered no assistance. The manufacturer referred the contact to the federal safety agency Hotline to report the failure. The approximate failure mileage was 120,700.

Filed Jan 14, 2025 · Engine · 111,000 miles · NC

The contact owns a 2018 Hyundai Santa Fe Sport. The contact stated while driving at an undisclosed speed, there was an abnormal knocking sound coming from the engine compartment. The contact stated that the vehicle went into LIMP Mode and inadvertently lost motive power. The contact was able to pull over to the shoulder of the roadway, where the vehicle failed to restart. The check engine warning light was illuminated. The vehicle was towed to the dealer, and the contact was notified of a misfire in cylinder #1 and #2 which caused damages to the engine. The contact was informed that the engine needed to be replaced. The vehicle was not repaired. After investigating the failure, the contact related the failure to the federal safety agency Campaign Number: 20V746000 (Engine), but the VIN was not included. The manufacturer was notified of the failure, a case was opened, and the contact was referred to the federal safety agency Hotline for assistance. The failure mileage was 111,000.