NHTSA Complaint #11701594 — 2015 HYUNDAI SONATA

I heard noises immediately after purchasing the Sonata. I took it back in to Carmax ( where I bought it from) multiple times and was told they didnt find anything wrong. As time went on, I took my sonata to Hyundai dealer to get checked out. 1st time they told me, Hyundai wouldnt cover the cost to check out engine & that it would be $700 to take a look. The 2nd time, I was told we cannot check it out because the engine light isnt on. Basically they couldnt scan/check codes without the light being on. I suggested that if they just rode around the block, that they would notice that there's an issue. They still said no. Then back in February, I took back to Hyundai dealer again & they did check it out because the engine light was now on. That inspection came back as the cylinder was bad. Hyundai doesnt cover it because at that point it was past 100k miles and I was not the original owner. I asked about 100 mile.warranty when I bought it at carmax and was told yes 100k warranty still applies. So upon further research, hyundai has had problems with this year/make/model/ engine type before. If they knew something was wrong with it, why not just say so & fix it? Or as soon as I seen the first issue, check it out and repair it for me?