On Hot days (> 90F/32.2C) I have fuel leaking from a canister behind the fender on the drivers side of the vehicle. This canister can be seen if you open the drivers door and look forward, between the hinges. It will leak about 1/4 cup of fuel before it stops. The dealer spent 1.5 hours checking it out, pressuring the system, but cannot locate any problems. A couple of other facts. The gas tank was filled, but driven about 30 miles/48 km, and there is an elevation gain from 5500ft/1676m to 7200ft/2195m. The only thing the dealer could guess was that the gas expanded due to the heat. It doesn't seem safe to me to have a vehicle leaking gas. Additionally, before the gas comes out, the engine will run rough, dropping frequently from 2000 rpm to 1500 rpm, like it might be going to quit, but catches and keeps going. However, this isn't setting any codes for the dealer to retireve.

Any thoughts about why this is happening? The only thing I can do now is not fill the tank up, but to only fill it 3/4 full.