Hyundai Santa Fe misfire problems

Filed Nov 1, 2026 · Engine, Fuel system · NJ

For approximately the past year, my 2021 Hyundai Santa Fe, currently with about 23,000 miles, has experienced intermittent engine and fuel-system problems. During start-up, the vehicle sometimes makes an abnormal rattling/cranking noise, followed by noticeable engine and vehicle vibration. Warning lights may appear, and on some occasions the engine does not start successfully on the first attempt. When it does start, it may initially run rough. The vehicle has also stalled intermittently and has had repeated incidents where pressing the accelerator produced little to no engine response or acceleration. This creates a serious safety concern because the vehicle may unexpectedly stall, lose power, or fail to accelerate when needed while driving. The vehicle has been at an authorized Hyundai dealership for more than one month. The dealership has been working with Hyundai Tech Line and has replaced or evaluated the low-pressure fuel pump, high-pressure fuel injector, high-pressure fuel pump, MPI/port fuel injector, and valve cover. The latest recommendation is to drain, clean, and refill the fuel tank. Despite these repair attempts, the root cause has not been clearly identified or permanently resolved. I am concerned that the repair process has become trial and error, with additional components being replaced while the underlying safety-related issue remains unresolved. I am also being asked to pay out-of-pocket for some of these unsuccessful repair attempts. The vehicle is currently at the Hyundai dealership and is available for inspection if needed.

Filed Sep 27, 2026 · Engine, Transmission · MD

Immediately following the mandatory Hyundai Servie Campaign Update 9C2-ECU THETA 11my vehicle began exhibiting severe hesitation, very rough idling, jerking at slow speeds and when gear changes, difficulty going up inclines and almost feel at times as though it is about to lose power which poses life threatening situations especially when turning into traffic. I have reported it to the dealers who never once test drove the vehicle but said to me that they did and could find no problem, however they did make me pay for repairs which never fixed the problem. I returned three times with the same issue. They recommended a Fuel Induction Service and a Auto Trans Service. Spark plug change. Igniton coils change. Nothing worked!

Filed Sep 8, 2026 · Engine · PA

-The primary mechanical failure is a burned exhaust valve in Cylinder 2, which has resulted in 0 PSI compression and a persistent engine misfire. This severe top-end valve degradation occurred as a direct consequential result of a chronic, underlying defect in the engine's internal oil-delivery and consumption systems. The vehicle is currently fully assembled, intact, and available for immediate inspection upon request at Brown-Daub Hyundai. -The vehicle suffered a sudden, severe loss of motive power while operating in traffic due to the cylinder drop, triggering a sudden transition into a dangerous operating state. The extreme oil consumption rate (burning 5 to 6 quarts of motor oil every 3,000 miles) created an ongoing, severe risk of sudden highway stalling, catastrophic moving component seizure, and potential engine bay fire due to extreme internal operating friction and chronic oil starvation. -Failure has been confirmed by two independent automotive facilities: Independent Confirmation: On XXX, [XXX]’s Service Center performed a diagnostic scan and an engine compression test, formally documenting diagnostic trouble code P030200 (Cylinder 2 Misfire) and verifying 0 PSI compression in Cylinder 2.Dealership Confirmation: On XXX, the service manager at Brown-Daub Hyundai executed a formal electronic and mechanical inspection under Repair Order #XXX, duplicating the failure and logging active trouble codes P0301, P0302, and P0128. -Symptoms first appeared progressively through an accelerating, severe oil consumption defect, which was documented during multiple routine maintenance: XXX oil consumption (115,865 mi): XXX (119,601 mi) no external leaks: XXX (125,502 mi) excessive oil consumption:XXX (135,116 mi) excessive oil consumption:XXX (133,022 mi) P0420 Cat Code: XXX (approx. 137,000 mi)engine rough-riding, shaking, & violent misfires began, preceding the mechanical breakdown INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Aug 28, 2026 · Acceleration, Engine · TX

While operating the vehicle, the vehicle suddenly began severely hesitating and stalling. During the incident, engine RPM surged to approximately 6,000 RPM and accelerator pedal response became abnormal. The vehicle was not responding normally to accelerator input, which significantly affected the ability to operate the vehicle safely. The vehicle subsequently recorded diagnostic trouble code P0304 – Cylinder 4 Misfire Detected. The abnormal operation of the vehicle during the incident was also captured on video. The vehicle was taken to an authorized Hyundai dealership for diagnosis. The dealership has advised that because the condition is not currently occurring and they have been unable to duplicate the problem, they may be unable to diagnose or repair the vehicle. The safety concern is not simply an illuminated check-engine light or a stored P0304 code. The concern is the combination of severe hesitation/stalling, abnormal accelerator response, and the engine surging to approximately 6,000 RPM while the vehicle was being driven. The cause of the condition has not been identified and, at the time of this complaint, the vehicle has not been repaired for the underlying problem. I am concerned that this condition could recur without warning while accelerating, entering or crossing traffic, or traveling at highway speeds. A recurrence could result in an inability to accelerate normally, unexpected vehicle behavior, loss of normal vehicle operation, or a collision. Hyundai has been notified of the issue and I have requested further technical investigation of the engine misfire as well as the transmission/TCU and electronic throttle/accelerator systems due to the high-RPM event and abnormal accelerator response. I am submitting this complaint because this appears to be a potentially serious safety-related defect and I want the federal safety agency to have a record of the incident and determine whether similar stalling, high-RPM, acceleration, transmission, or engine-misfire.

Filed Jul 15, 2026 · Engine · MA

After having the Service Campaign 9C2 ECU SOFTWARE UPDATE FOR THETA II EMISSIONS IMPROVEMENT, TSB 26-01-013H-2 done, my vehicle started having driveablity issues. On a normal, cold start the engine's RPMs go up really high, so I take my foot of the gas and the revs drop, almost stalling the car, and then the car bucks. I put my foot back on the gas pedal, and the engine revs really high again and takes off. If I try to drive normally, the car bucks and runs rough. My car also revs a lot higher during highway driving, than it did before the update. All of this is also causing terrible gas mileage. My car did nothing like this until I had the 9C2 update.

Filed May 24, 2026 · Engine · CA

The engine in my 2017 Hyundai Santa Fe Sport equipped with the 2.4L Theta II GDI engine is experiencing severe excessive oil consumption. The vehicle consumes approximately 2–2.5 quarts of oil every 1,000 miles despite multiple repair attempts and dealership-performed combustion cleaning procedures. Hyundai Motor America and the dealership documented the condition under PA #[XXX] and recommended engine replacement. Hyundai Motor America advised me in writing that the vehicle should not be operated in its current condition because of the excessive oil consumption and pending engine replacement. Excessive oil consumption creates a risk of sudden engine failure, engine seizure, stalling while driving, and potential engine fire if oil levels drop unexpectedly. Because the engine rapidly loses oil between normal service intervals, the vehicle may become unsafe to operate without warning, placing myself, passengers, and other motorists at risk. The defect was confirmed multiple times by Capital Hyundai in San Jose, CA through two official Hyundai oil consumption tests. The dealership documented oil consumption of approximately 2–2.5 quarts per 1,000 miles and submitted the results to Hyundai Motor America under PA #[XXX].The dealership also performed multiple repair attempts, including spark plug replacement, fuel induction cleaning, combustion chamber cleaning, and repeated oil changes, but the excessive oil consumption continued. Prior symptoms included: Check engine light illumination, Cylinder #4 misfire condition, Engine noise, Excessive oil loss between oil changes, and Oil level dropping significantly within short mileage intervals. The check engine light and misfire condition first became severe enough to require dealership diagnosis on or around [XXX], when the vehicle was towed to the dealership. The excessive oil consumption issue was formally documented beginning [XXX] during Hyundai’s oil consumption testing process. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6

Filed May 24, 2026 · TX

Two unsafe scenarios in past two months: 1) Driving 80 mph, engine misfire, vehicle will not accelerate past 1 rpm, had to drive home from out of town with very slow acceleration, dangerous to not be able to accelerate efficiently on highways 2) Driving 55 mph, all driver safety systems malfunction, accelaration completely disabled, had to coast to safe stopping point. Restarted vehicle and could drive home with check engine light on, incredibly dangerous for car to lose all ability to accelerate in the middle of a highway.

Filed May 11, 2026 · Engine, Fuel system · FL

My 2021 Hyundai Santa Fe (VIN [XXX] ) is experiencing severe engine instability, including rough idling, hesitation upon acceleration, and intermittent stalling. These symptoms align with TSB 26-FL-001H regarding defective GDI fuel injectors. The vehicle has stalled in traffic, creating an immediate risk of a rear-end collision. Despite being within the 100,000-mile Powertrain Warranty, the manufacturer is refusing to perform the required diagnostic tests (GDS Fuel Pressure Drop Test) to identify the leaking injectors. This failure to diagnose a known fuel system defect poses a significant safety risk to the driver and other motorists. The primary safety risk is unexpected engine stalling while the vehicle is in motion or stopped at intersections. Additionally, the loss of power during acceleration prevents the vehicle from safely merging into high-speed traffic, significantly increasing the likelihood of a collision. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed May 1, 2026 · Engine · 87,000 miles · AR

The contact owns a 2017 Hyundai Santa. The contact stated that while driving at approximately 55 MPH, the vehicle stalled and hesitated to accelerate while the accelerator pedal was depressed. The check engine and check engine oil warning lights illuminated. The vehicle was taken to a local O'Reilly's, where it was diagnosed with ignition coil #3 misfire. The vehicle was not repaired. The vehicle was towed to an independent mechanic, where it was diagnosed and determined that the engine needed to be replaced due to severe engine oil consumption. The vehicle was then to a local dealer, where it was diagnosed with abnormal engine oil consumption, and the dealer determined that the engine needed to be replaced. The vehicle was not repaired. The contact stated that the vehicle required an engine oil refill 800-1,000 miles before an engine oil change was due. The contact related the failure to several unknown Hyundai TSBs. The manufacturer was made aware of the failure, and a case was filed. The failure mileage was approximately 87,000.

Filed Feb 16, 2026 · Fuel system · FL

In November 2025, my 2022 Hyundai Santa Fe began to hesitate when accelerating and would almost "jerk" when I pressed the gas pedal. Soon after my check engine light came on and I made an appt to take it for the closest Hyundai dealership (as it's still under warranty 33k miles) Upon running a check the dealership notified me that Fuel Injector 1 has misfired and will be replaced. I receive my vehicle back and not even 100 miles later my check engine light in on again and the same issues are arising. Back to the dealership to see now Fuel Injector 3 has misfired and there is an open TSB showing all 4 Fuel Injectors need replaced. My vehicle was finally returned to me in January 2026. It is now February 16, 2026 and my check engine light in on YET AGAIN. I've been given the run around from Hyundai Corp about fixing this vehicle. Why is this acceptable treatment when a vehicle is under warranty ?