2018 HYUNDAI SONATA Fuelpropulsion System Problems

While driving on the highway, my 2018 Hyundai Sonata experienced sudden loss of engine power and became undrivable. The failure occurred without warning at approximately 86,500 miles. At the time of the incident, there were two children in the vehicle, and the breakdown occurred at night in cold temperatures (approximately 20°F). An authorized Hyundai dealership later diagnosed zero compression in cylinder 3 and confirmed a cracked piston, recommending full engine replacement. The sudden loss of power while driving created a safety risk due to traffic conditions and environmental exposure.

I am submitting a formal complaint regarding ongoing and severe engine issues with my 2018 Hyundai Sonata SE. Despite proper maintenance, the vehicle has developed extreme oil consumption and misfire problems that have made the car unreliable, unsafe, and financially burdensome. Beginning around 118,000 miles, the vehicle started consuming oil so rapidly that I was forced to completely replace the oil every 1–2 weeks because it would run dangerously low or nearly empty. This level of oil loss is not normal, acceptable, or sustainable. I have detailed documentation, receipts, mileage logs, and maintenance history supporting this. In addition to oil consumption, the vehicle has repeatedly misfired, produced diagnostic trouble codes, and fouled spark plugs with oil. I have been forced to replace spark plugs approximately every two weeks, which is clearly abnormal for any modern vehicle. On multiple occasions, the vehicle has experienced violent knocking noises, severe loss of power,...

Unknown. 2018 Hyundai Sonata engine has failed. Only purchased the vehicle in December 2024, and the engine is defective. There is much information, via research, indicating that Hyundai is aware of the engine issues with this year vehicle, but are unwilling to make amends. Vehicle has 100,189 miles.

Oil consumption was ridiculously high, changing oil/topping off oil constantly. Car would not accelerate over 30 mph without sputtering and rumbling. I had mechanic diagnose bad sparks plugs due to sitting in oil from leaking. After I had them repaired/replaced the car drove great for 1 day, then decided to die in the middle of a busy intersection while I had my teenage son in the car with me. My son and I had to PUSH it out of the busy intersection onto a side street to get out of the way! I had it towed to Hyundai dealer who said the spark plugs were bad and that the fuel pressure sensor and gdi pump were faulty and needed replacement. Left front lower control arm/ball joint assembly also requires fix. To the tune of $3000 + . It’s been at dealer for past few months until I can afford the...

The fuel pump filter housing is the cause of the malfunction, it is available for inspection upon request. When I am driving I intermittently lose fuel delivery altogether and my car comes to a halt for a second until I press on the gas pedal to get the car going again, this puts myself and other people in danger if my car randomly stops while I am driving around others and causes crash risk. An independent service center ran a diagnostic and stated it was the fuel pump filter housing. It has not been inspected by the manufacturer, police, or insurance reps. But it has been inspected by the service center near me. An engine code was produced that pointed to the gas cap, but the gas cap was fine, which indicates fuel delivery issues. There was also shaking during acceleration prior to the incident happening. My VIN does not...

Urgent Complaint About Repeated Engine Issues on 2018 Hyundai Sonata (VIN: [XXX] ) Hello, I’m writing to file a formal complaint regarding a 2018 Hyundai Sonata, VIN [XXX] , currently financed and still owing $9,700, but the vehicle is no longer reliable or functional. For over a year, the car has had constant mechanical issues, primarily: •Spark plug failures within weeks of replacement •Repeated misfiring •Constant oil consumption — requiring oil refills every few days •No clear cause ever detected by diagnostic machines Despite replacing the top engine cover, spark plugs, filters, and performing other repairs, the car continues to break down and remains unsafe to drive. These issues began shortly after the 2-year warranty expired in 2023, and have escalated rapidly. This has caused severe financial hardship for my family, who still have to pay nearly $10,000 on a loan for a failing vehicle. I am requesting Hyundai to...

The engine shuts off, doesn’t start, check engine light flashing, losses power, jerks while driving it, i will get it up yo speed then will shut off or won’t move.

Multiple critical mechanical and safety issues have occurred with my 2018 Hyundai Sonata Sport. The vehicle has experienced persistent engine misfire, a severe oil leak, emissions system failure, and extensive paint deterioration. A certified technician confirmed an active oil pan leak with no dashboard warning lights, posing a fire and stalling hazard. To prevent further damage, I replaced the entire oil pan and spark plugs at a personal cost of approximately $800 at Firestone Complete Auto Care. The check engine light revealed diagnostic code P0420 – Catalyst System Efficiency Below Threshold (Bank 1). An O’Reilly emissions scan confirmed the catalytic converter failure, and emissions status was marked “RED.” The vehicle will not pass an OBD-based emissions test. At 149,219 miles, Hyundai refused warranty coverage due to mileage. A certified Hyundai dealership quoted $3,722 to replace both the catalytic converter and valve cover gasket, which remains unaffordable and unrepaired. In addition,...

Burns oil fast. 900 miles from an oil change the car oil stick was empty. There are no signs of oil leaking. Every 1000 miles you have to place oil back into it. I’m not the only one complains of this issue. I was reading on Reddit and it’s thousands of people having the same issue.

My 2018 Hyundai Sonata (approx. 60,000 miles) began consuming excessive oil, and the engine started smoking while driving. My wife barely made it to the dealership — the car was unsafe, struggled to stay running, and visibly smoked from under the hood. Hyundai acknowledged the oil issue but refused to cover engine replacement. Instead, they approved a one-time combustion chamber cleaning and requested we drive the car 1,000 miles to "see if it gets better." This is a major safety concern. The vehicle is part of a group of Hyundai models known to have defective Theta II engines that have led to engine failure, fire risk, and recalls. This issue is widespread, and Hyundai is not taking proper responsibility for defective engines in cars like mine.

- Component or system that failed: engine (cylinder #4 misfire) - Safety was put at risk twice: once when knock sensor went off on interstate (October) and engine went into limp mode (aka protection mode). Required a tow from the, which was tricky with a vehicle full of passengers. Safety was put at risk gain when vehicle began to stutter/sputter on interstate (December). Drove 4-cylinder vehicle essentially on three cylinders an hour to dealership - Problem has been confirmed by dealer (Southern States Hyundai, Raleigh, NC) - vehicle has been inspected by warranty inspector, who requests approval before disassembling engine to diagnose issue. However, based upon maintenance records and manufacturer's history of engine issues (more on this below), owner should not be liable for investigating a well known issue. At the time of this writing, the issue has been escalated beyond the dealership and warranty to Hyundai Motor America, and...

The motor blew in my 2018 Hyundai sonata due to a manufacturing defect. There was a recall on it a couple of years ago. They acknowledged it was a defect which is why they put an extended warranty on the engine. Because I could not come up with maintenance records dating back until 2018 (I only had them dating back to 2020), they denied my motor and will not fix it. I bought the car brand new in 2018 and have had nothing but issues ever since. I have had to change the oil in this vehicle every 2 weeks, because it would be nothing in the oil tank at all. When the recall come out, they said they could not fix the vehicle until the motor was blown. Now that the motor has blew, they won't fix it because I don't have repair records dating back 6 years ago.

I own a 2018 Hyundai Sonata 2.0 turbo I paid cash for it in [XXX] with 2011 miles on it for 24,000 cash didn’t start having problems until 2022 then the I kept hearing a knocking on the left front wheel. I had it look at several places because the Hyundai of Louisville dealership kept telling me my title was branded I didn’t know what that meant till I took my title to the tag office and had the sheriffs department check the title out and it was an still is 100 % clean then my engine kept getting worse an in may of 2023 the engine stopped working I had the car towed to the local dealership and they couldn’t even look at it till Aug of 2023 the they told me I shot out a code 99 and they refused to update my software for the knock sensor...

The car was sitting in the parking lot and randomly black smoke started coming from it and then it turned into fire within in minutes. No one was in the vehicle and 911 was contacted.

Car consumes TOO much oil. Even after I get an oil change I have to add more oil weeks later and the oil is always black. Several times the sensor has gone out on me on the hwy and I’m not able to accelerate or go over 35 miles which is extremely dangerous .

Fuel pump started going out. My brothers vehicle also started going out too in the same vehicle as this. It's clearly a wide issue. Car stalls when gas is at half tank.

Knocking of the engine , engine light continues flashing , lack of acceleration finally feb of this year the turbo blew up an the car stop running all symptoms of knock sensor problems . I’m Taking it to Hyundai on Dixie on Monday in two days an I hope they don’t deny the federal recall an I will have to have a loaner car . They have told me the last 5 years my title was flawed last month they denied saying that an told me my warranty was voided with 41,000 on my car

Engine takes a long time to start up, about 10-15 seconds of pushing the start button starts engine which is probably not good for the car. Also, the car jolts/ wants to stop while driving. Has been an ongoing issue since the week of 9/5/22. Loss of motor power issue sounds like what is going on with my 2018 Hyundai Sonata vehicle.

My 2018 Hyundai Sonata GDI Engine stop working while I was driving on the freeway without a warning prior to the issue. It never gave me a heads up in advance that the engine needed service. No check engine light to alert me that an issue needed attention. I learned about the engine problem when my engine stop working while I was on the freeway. I heard a loud noise coming from the engine and within seconds my RPM started going down and my car started loosing power while I was driving on the freeway. At the same time my check engine light came on and it was flashing. At that moment I realize something bad was happening with my motor. The check engine light was not on before that. It never alerted me before that, and when it came on flashing on and off it was already too late...

On May 03, 2022 at approximately 3:30pm I was traveling southbound on Arizona State Route 101 in Tempe, Arizona. I was going about 75 mph, and without no warning my car shut off. I had to pull off to the shoulder of the highway to avoid being struck by other vehicles, and also incase I lost control. My Hyundai picked up nails on 3 of the 4 tires in the process. I barely avoided a fatal accident due to the defect, which I had no idea about.

IN FEB 2020 MY SONATA WENT INTO SAFE MODE AFTER EXITING HIGHWAY AND DEALER ENDED UP REPLACING "KNOCK SENSOR". IN DECEMBER 2020 MY ENGINE "STUTTERED" THROWING ME FORWARD AS IF I HAD HIT BRAKES HARD. NO WARNING LIGHTS OR MESSAGES OCCURRED AND AFTER A FEW SECONDS CAR ACTED NORMALLY MOSTLY. A FEW DAYS LATER AFTER EXITING HIGHWAY AGAIN THE ENGINE WARNING LIGHT (ORANGE) CAME ON ALONG WITH ERROR MESSAGE "POSSIBLE CONDITION WITH ENGINE CONTROL SYSTEM" HAS BEEN DETECTED. CAR DID NOT GO INTO "SAFE MODE" AND SEEMED TO BE OPERATING NORMALLY. I CONTACTED DEALER WHO ASSURED ME SAFE TO DRIVE OVER HUNDRED MILES BACK TO DEALERSHIP IN THIS CONDITION TO CHECK. I DROVE BACK FROM EAST COAST FL TO WEST COAST FL TO TURN CAR IN. I BELIEVE ENGINE ISSUE EXPERIENCED IS RELATED TO THE THETA ENGINE ISSUE AND REPAIR WOULD BE COVERED UNDER SETTLEMENT. DEALERSHIP DISAGREES AND HAS INDICATED...

MY 2018 SONATA WILL NOT START WHEN TEMP DROPS BELOW 20 DEG F. IT HAS HAPPENED 3 TIMES THIS WINTER AND WHEN IT WARMS BACK UP TO 40 TO 50 DEGREE IT WILL START. WHEN I TURN THE KEY ON ALL THE LIGHTS ON THE DASH LIGHT UP LIKE NORMAL. I CAN MOVE HEAR SELECTOR AND TURN WHEEL. BUT THE STARTER WILL NOT ENGAGE NOTHING IS HEARD NOT A CLICK OR A SHIRT. IS THIS COMMON PROBLEM?

THROTTLE RESPONSE: FEELS LIKE THE OLD VEHICLES WITH A FLAT SPOT IN THE CARBURETOR ACCELERATOR PUMP. THE "THREE SECOND' RULE APPLIES WHEN THE THROTTLE PETAL IS PUSHED. THERE IS A SERIOUS HESITATION AS THE ENGINE TENDS TO FALL FLAT BEFORE ACCELERATING. HAS TO DUE WITH THE SIX SPEED AUTOMATIC TRANSMISSIONS DUEL CLUTCH WHICH ACTS AS IF A PERSON WERE OPERATING A STANDARD TRANSMISSION CLUTCH. I HAVE DISCUSSED THIS PROBLEM/CONCERN SEVERAL TIMES WITH THE SERVICE DEPARTMENT WHERE THE VEHICLE WAS PURCHASED. THE SERVICE DEPARTMENT INDICATED THEY RECEIVE NUMEROUS COMPLAINTS. IT IS INDICATED THE DRIVERS EITHER LOVE THE VEHICLE WITH THIS PROBLEM OR HATE. WE WERE NEVER TOLD OF THIS SITUATION. AND THERE IS NO FIX FOR THIS. THIS SITUATION CAN OCCUR WHEN LEAVING A STOPPED POSITION, WHEN TURNING RIGHT OR LEFT FROM A STOPPED POSITION, ACCELERATING UP A HILL IN MOVING TRAFFIC OR ON A STREET. THIS ALL DEPENDS ON THE...