The contact owns a 2021 Hyundai Tucson. The contact stated that while driving 35-45 MPH, the vehicle shut off unexpectedly. There was an abnormal rattling sound coming from the vehicle. Additionally, the contact stated that the vehicle failed to accelerate while driving. There were no warning lights illuminated. The vehicle was taken to the local dealer where it was diagnosed that the rod bearing and the engine needed to be replaced. The vehicle was repaired; however, the failure recurred. The vehicle was taken to another local dealer, Hyundai of Orange Park (7600 Blanding Blvd, Jacksonville, FL 32244); who determined that the coils needed to be replaced. The vehicle was not repaired. The vehicle was taken to an independent mechanic who replaced the coils and determined the failure was due to the engine. The vehicle was repaired, but the failure reoccurred. The manufacturer was contacted, but no additional assistance was provided. The failure mileage was approximately 124,500.