Hi,this morning i ran to the store and while in idle and shut off.i crank it up with no problems and i went home.i had to leave again and while letting it warm up again a bit i was running the back windshield wiper and pushing the fluid button but it was dry so i stopped and the truck cut off again.i cranked it up with no problems again.i know it could use that emissions thing/valve but im not sure what would cause this and im worried it may get worse.i always use bp gas but i think the other day i had put some cheap gas in due to lack of money.does anyone have any ideas to what may be causing this?thanks.