See the Da’as Zekaynim (found in a Mikra’os Gedolos), where he explains that Eisav was 13 when he started avodah zara, and Yaakov was 13 when he went off to the beis medrash. He says that Eisav rebelled for 2 years while Avraham Avinu was still alive.
He also brings down the Yerushalmi who asks this question and answers that from 13 to 15, Eisav rebelled privately/bi’tzinah, but at 15 started serving avodah zara openly/bi’farhesya. It seems to be unclear if Avraham’s death spurred Eisav, or if Eisav’s open rebellion spurred Avraham’s death.