So I recently got the Hyundai and when I got it there was nothing wrong. Now I looked under the hood and it seemed to be like there was white powdery substance everywhere. Also the ac smells really bad when I turn it on. Anything thing is the muffler/ exhaust pipe when I stuck my finger in it I had black substance all over my finger. But when I got the car the exhaust pipe was clean.
My car has 128000 miles.
My car has an automatic transmission.
I am not sure what the white power is but suspect it was from the chemicals used to clean the engine has caused some sort of chemical reaction on the metal parts of engine. I recommend having the engine cleaned with a soap designed to clean motors and rinse engine good with clean water on low pressure and let dry overnight before driving if you can. Do not use high pressure or may get into wiring connectors and ignition system causing problems. On the black residue on the inside of tail pipe you may not have a problem and is normal unless you have problems with check engine light on or poor fuel mileage then you should be okay.