i was driving my moms nissan altima on a road trip and the car is nice. its the 2.5 liter v4 model. i stopped to get a drink and smelled burning rubber, it wasnt a strong smell but it was there. i popped the hood and the engine liiked like puzzle to me because im used to american cars. i checked the engine temp and it was half way between hot and cold, so normal. what could it be?