High fuel consumption and a slight mis

My car is using hundred miles per tank less than I was getting a few has no kickdown power will not get up and go other than that runs fine seems like what sensor. What would I check first or what would I cause it to drink that much fuel and still run decent. I can notice a slight mis in it running down the highway almost free floating engine light bounces off and on, when I kick it down and let up on it then the light will go off. It is just drinking lots of fuel other than that seems to run fine other than kick down. It will not get up and go.