NHTSA Complaint #11679724 — 2023 KIA RIO

I’ve been hearing this rattle noise mostly when I crank the vehicle. I took it to go get checked out and they heard it when I first brought it in for them to check. But when they got it to the back for mechanic to listen for it, of course it didn’t do it. They kept my car a whole day to try n find the issue/hear the noise and was unsuccessful. I’ve been told that it could possibly have something to do with the car timing or something with the engine. My car only has 34000 miles on it and it’s making this noise. They won’t approve me to trade it in or anything to help fix the problem or get me in something better.