1999 Nissan Sentra stalling problem

#1

Friend has a '99 Sentra with 200K. She has serviced it regularly over the years. Lately, the car is stalling at red lights, intersections. She can start the car easily after the stall, though. She says she smells gas fumes at times and also noticed a hissing sound near the rear wheel. Any ideas on the problem(s)? Thanks for your help!

#2

So this only happens once the car is warmed up or something? Will it idle when first started?

Starting with cleaning the idle air control valve (IAC) would be good.