[dwill3015]

Hello Leo and welcome to the site! We are very sorry to hear your Avalanche is not running properly. Can you gave us anymore information or describe how it is running? If it is the 5.3 liter engine, it could be running roughly due to a plugged fuel filter or bad fuel pump. Or, it could be elctrical and running roughly due to a bad coil pack giving ramdom mis-fires. I hope we can help!