I was trying to pass someone today and get into the next lane. When I put my foot on the gas instead of picking up speed it slowed and then shot forward. I can only explain that it kind of surged. I noticed later as i was driving that this did this more subtly. Essentially acceleration is just not very smooth. With the prior incident being this issue in the severe. The car has 90k miles on it. Any idea what is going on? What kind of repair it may need? Cost of said repair? Is this an indication of something very bad or something very simple? I am trying to think about going down to one car and since this car is paid for and low mileage I wanted to keep it, but if this issue is something that might end up being a nightmare. I am nervous. Thanks anyone for your help and input.