Why when coming to a stop hummer turns off?

Hello, shame on Auto Zone for giving you wasteful bad advice. Your fuel cap can never, ever influence an engine stalling condition. You'll need to have diagnostic testing performed while the problem is occurring to find out if you are losing fuel delivery, have a bad fuel - to - air mixture ratio, or have an ignition spark issue. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops