2002 Ford Escort Question: My 2002 Ford Escort,will crank but not start.

We have fuel, air, and spark, but it will not start. It acts like it wants to, but won't catch. It is a 4 door sedan, 2.0 liter engine, auto transmission. We have been told it's the computer that's bad, but we're not sure. Could it be the Control Module (or IS that the computer)? It has been running rough and hard to start for a week, and Sunday it refused to start at all.