Not sure if I'm too late to help, but this happened to my 2001 and the culprit was a faulty gas cap. I guess there is some pressure sensitive check valve in there that was stuck open. Might want to invest $15 in a new one before spending any $$ at the dealer.

Good luck.


2001 Silver 4Runner, Nokians, Thule rack
2003 Red Tacoma Extended Cab, V6, 5-spd