We have a 2006 Tucson. When we back up it just dies. I have notice at high speeds it seems fine. On start up it idles hard. When trying to pass on the highway it seems to hesitate then it kicks in. There is no check engine light and we had the same issue two months ago and the dealership did a engine flush. It seemed to help until now. I am thinking there is more that needs to be done. Can anyone help??