My 2005 Tucson GLS, with the 6 cylinder engine and automatic, is stumbling badly when accelerating from a stop. I put my foot on the gas and the car lurches while the tach swings up and down between
1000-2000 rpm. This started after my last fill up, so it may be a bad tank of gas. I have an appointment with the dealer for next week.Any ideas what I might be looking at?