Today i went to get gas and my car wpuldnt start. For a few dasy i have been hearing a slight knocking sound and when i stepped on the gas it seemed to get a little louder and faster. Then a couple days after that started when i would start my car it would start and then idle real low like it was gonna die then it would be fine. Today it did the same thing but it actually did die and now it wont start. It turns over and starts but immediately dies. The knocking is a thousand times worse. I need an oil change but its only been about 4000 miles and there is plenty in there. I dont know whatvhappened and i need to fix it fast. i deliver pizza and now im out of work. Ots a 2002 ford focus with 120000 miles on it. Can anyone help??