Engine was just replaced in January and had 140000 miles on it. Over the past month or two my car has been acting funny. It doesn't want to accelerate so you have to gradually push the gas pedal down and then it like jolts and takes off. Today I was driving my car and it just stopped running so I coasted into a parking lot. I tried to restart it and it sounded like it wanted to start but wouldn't. What could the problem be?