My 2004 SES would crank but not start. I have 3 keys so I thought I'd try another and see what would happen. The car started right up. I figured I had a bad key so I changed keys and hung the "bad one" in the garage. A week later the car would crank but not start again. I tried a third key and the car started. Then I tried the 1st key just to see what would happen and the car started. This cycle seems to change like the weather as one week one key works and the next week a different key works. I've already had to try all 3 keys till the car started. If I ever need a 4th,I'm screwed. I only have 3. I haven't found a mechanic at a Ford dealer yet that has ever run into this problem. I could use some help.