I bought a 2000 Ford Contour about 6 months ago. I had problems at first when it got down to under a quater of a tank of gas and it would die. Then it gave me problems a little over a quater. Then about 2 weeks ago the CEL came on and it is running rough. I had the cam sensor changed, because that is what the machine said to do. It ran fine once driving it, but after turning the car off and then back on the CEL came back on and it is running rough again. There is a noise coming from the engine. It is showing the cam sensor again. And also says the Fuel system is closed. Any Suggestions?