2018 Hyundai Santa Fe Sport: sudden loss of power

Filed Oct 5, 2026 · Engine · WA

While driving over the pass the car suddenly lost power and was running very rough. Luckily there was an exit close by that we took and the engine died on the exit. We were able to get it started and get to a parking lot where it died and would not start again. While trying to start it in the parking lot the check engine light came on. So, after a $375 tow to the nearest town the mechanic discovered a damaged spark plug and the compression test showed 0 psi. The scope showed a hole in the piston. The car also leaks and burns oil. The mechanic recommended scrapping the vehicle since it would not be cost effective to repair it. The mechanic said ours is the 6th Santa Fe in their shop with a blown engine in the past month. It has not been inspected by anyone else.

Filed Sep 15, 2026 · Engine · NE

My 2018 Hyundai Santa Fe Sport (2.4L Theta II GDI, VIN [XXX], approx. 110,000 miles) has suffered a chain of engine and emissions-system failures that create a loss-of-power safety hazard. At about 80,000 miles, Hyundai replaced the original engine under warranty for excessive oil consumption, a defect Hyundai has acknowledged across the Theta II engine family. After only about 20,000 miles on that replacement engine, the catalytic converter failed and set a P0420 code. The vehicle now bogs down, hesitates, and loses power under acceleration. This is dangerous when merging or accelerating into traffic, where a sudden loss of power raises the risk of a collision. A restricted or failing catalytic converter causes exhaust backpressure and abrupt power loss, and the underlying oil consumption also risks low-oil engine damage and stalling. A catalytic converter should last far longer. This premature failure is consistent with the well-documented Theta II pattern in which engine oil consumption contaminates and destroys the converter substrate. It indicates the replacement engine Hyundai installed is itself consuming oil and damaging downstream exhaust and emissions components. I reported this to the dealer and to Hyundai. Hyundai declined to cover the catalytic converter, treating it as unrelated, even though its own warranty engine replacement is the direct cause. I am filing so this safety-related failure is documented. No crash, fire, or injury has occurred. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

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 Apr 16, 2026 · Engine · NV

While driving on the highway at approximately 70 mph with a heavily loaded vehicle, my 2018 Hyundai Santa Fe Sport 2.4L suddenly lost power and entered limp mode. The check engine light flashed and diagnostic code P1326 was stored. During limp mode the engine was banging hard, almost like it was seizing and then releasing repeatedly. This is consistent with connecting rod bearing failure, not wrist pin failure. P1326 is generated by Hyundai's Knock Sensor Detection System (KSDS), specifically designed to detect abnormal vibration consistent with connecting rod bearing failure — a known defect covered under Hyundai's Theta II engine warranty extension. Prior to this event the engine had been consuming oil abnormally. Approximately 1,300 miles after my last oil change the oil level had already dropped to the low mark on the dipstick, a significant change from normal operation. The vehicle was towed to a Hyundai dealership where it remains today. The dealership confirmed cylinder scoring and wrist pin damage. Hyundai is attributing the failure solely to wrist pin failure to avoid Theta II warranty coverage. I believe the wrist pin damage is downstream damage caused by the underlying rod bearing defect. My safety was directly at risk at highway speed. The vehicle has approximately 140,000 miles and is within the 15 year/150,000 mile Theta II warranty extension. A Warranty Prior Approval has been submitted to Hyundai Motor America and has been unresolved since March 24, 2026.

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 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 Mar 1, 2026 · Engine · MN

2/27/26 Kept regularly scheduled oil changes with dealer. Car began to knock and lose power, Oil light is periodically flashing on and check engine light came on. Took car to Valvoline oil change-they state no fluid on the oil dipstck. Scheduled oil change was not for another month. No oil leaks at all. Vehicle is bucking and knocking and loses acceleration. I have an appt at the dealer tomorrow3/2/26 and am hoping hyundai will cover any necessary repairs as they have multiple Technical service bulletins about this.

Filed May 23, 2025 · Engine · MI

Followed all the steps for the theta II engine issue included replacing the knock sensor and spark plugs. The engine lost power when driving to Chicago and had to get the vehicle towed and now the dealer is saying that I have to pay for the engine replacement at my own expense in Hyundai is not covering.

Filed Feb 11, 2025 · Engine · NY

What component or system failed or malfunctioned, and is it available for inspection upon request? The Engine with the 2.0T had a valve train malfunction possibly related to a bearing or other issues. Hyundai dealership did not determine the root cause and is denying engine replacement under the rod bearing warranty. Also as a 2nd owner they won't reimburse for any repairs. This vehicle was well maintained. 2018 with 90K miles. The engine is last known to be at the dealership but probably not available. I was not offered to get a 2nd opinion and the technician notes are vague in my opinion. How was your safety or the safety of others put at risk? While traveling on the interstate at 65 MPH the vehicle began to make a knocking noise and had a loss of power. The steering and breaking system also became difficult to use. I was able to get off an exit after only crawling along at a unsafe low MPH for the interstate. The vehicle stalled and lost all power while on the off ramp. I was able to glide to a stop and was ready to use the emergency brake. Has the problem been reproduced or confirmed by a dealer or independent service center? Hyundai's response is that it was in there opinion that the breakdown was not due to rod bearing failure however there is not a good diagnostics of a root cause. The failure was not due to poor maintenance. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? Just the dealership. Were there any warning lamps, messages or other symptoms of the problem prior to the failure, and when did they first appear? No warning lights. Sudden loss of power following by warning lights. Loss of power steering and brakes by the time the engine stalled.

Filed Mar 24, 2024 · Engine · KS

- I experienced an engine failure while driving. - I was in traffic the auto lost power and I had to immediately pull over. The immediate loss of power caused traffic to break. Fortunately, there was no incident but it could've been dangerous in a more congested area. - I had the vehicle towed to a dealership. - The dealership has looked at it. They submitted a report to the manufacturer over a month ago. - I saw the engine light flash and heard clattering coming from the engine compartment.

Filed Feb 27, 2024 · Engine · NC

During a dealer-suggested "oil consumption test" and driving down the interstate with cruise control on, SUV suddenly started experiencing reduced power and emitting a burning smell with no apparent warning lamps or messages. Exited the highway immediately and came to a stop on the side of the road and engine quit before even being able to put it in Park. Engine is 2.4L in-line GDI Theta II. Hoping to tow it to the dealer by week's end to have them pay for a replacement engine and get reimbursement.

Filed Feb 7, 2024 · Engine, Fuel system · FL

While driving in the Highway, my car lost engine power and lead to my car run no more than 40 miles per hour, after this I took my car to the garage and the said it was the knock sensor that course this issue. After being in the garage, my car knock sensor was replace for a new one to make sure this was giving good reads and while driving in a two way street it happen again and I believe this could be very dangerous if it happen while passing another car on in a crossway. Yes. Yes. As soon it happen the check engine light started blinking. It happens 3 times end of Nov 2023, early December and late December 2023.