Putting actual on-baord diagnostics in cars would be too much of a money loser for the car companies.They like the ambiguity and mystery of the CEL. Out of the multiple times my Contour has been in the shop in the 3 1/2 years I've owned it, I could've fixed the majority of the problems myself (most invloved replacement of a sensor) and saved a ton of money if I diagnosed it myself.
Go to Ford immediately. You most likely have some major problem that the computer is trying to warn you about. I had a problem with 2 cylinders not firing (plugs bad). No CEL, it just ran like **** and was really slow.