NHTSA Complaint #11484181 — 2014 HYUNDAI ELANTRA

I noticed a rattling noise while accelerating in second and third gear under my car in the spring. I took it in to a repair shop and they resecured an under tray but otherwise did not seem concerned. The rattling noise continued. After driving on a longer trip on the highway recently the rattling became more frequent and intense, causing the whole car to shake. I also had difficulty accelerating above about 50 mph. I took my car in to a different shop the following day. They discovered that there was a misfire occurring in cylinder 3, causing buildup in the exhaust system (the rattling that I noticed) and which caused the catalytic converter to go bad, which I had to pay to replace. Throughout this entire time, my check engine light never came on, although it illuminated normally when turning on the car. The lack of a warning via check engine light when the misfire began occurring caused the converter to go bad, resulting in a very costly repair for me.