NHTSA complaint #11654870

Owner complaint summary

One cylinder of the engine is misfiring. When I bought it used in 2021, I realized it had a problem. At red lights or stop signs, the car would randomly not accelerate when it was time for me to go. I would have to turn it off, then on; shift to park then drive; or mash hard on the gas for the car to recover. For example, it happened at these days and times in 2024 (I didn't write down every time since ownership began): 1/24/24 and the key icon lit up; 3/14/24 at 9:20 am; 4/20/24; 7/19/24; 8/7/24; 8/18/24; 8/21/24 at 10:40 am; 8/25/24; 8/27/24; 9/7/24 at 12:30 pm and 3:21 pm; 9/12/24 at 10:38 am; 9/20/24; 9/21/24 at 1:43 pm; 9/23/24 at 7:38 am; 11/12 at 9:36 am; 10/26/24; and 10/27 at 4:37 pm. It was scary! I took the car to the Hyundai dealership in September 2022 and in October 2022 for this issue and the alert that Forward Collision Assist warning wasn't working. I was told both time that they didn't know why the first happened and recommended I replace the entire bumper for the second (it's no longer happening and I did not replace the bumper). I reported it to Hyundai Customer Care and nothing happened. The car also required 4-5 quarts of oil every 2000 miles. I believe these were precursors to what happened this month. On April 5, 2025 the car completely stopped while I was driving on the highway. I added oil and it chugged to an oil change shop where the diagnosis was a problem with coil 3 in the engine. I went to an auto parts store and replaced coil 3, and the car chugged just enough for me to get home. I had a tune up and the mechanic put Heet in the gas tank in case it was a fuel injection issue. The car didn't improve so I took it to another mechanic who diagnosed a misfire in the third cylinder as well, and the spark plug in the third spot looked brand new though the other three showed a bit of wear from the few days I used the car. He told me the engine problem was serious and needed a dealer's examination. I will go to the dealership on 4/17/25.