1998 Chevrolet Metro

Engine Performance problem
1998 Chevy Metro 4 cyl Front Wheel Drive Automatic 77,000 miles

Hi. I haven't had any troubles with the car until now. Service Engine Soon light comes on. I took it in they said that the code said it was misfiring. The motor sounds like it's shaking and it backfires pretty good. Checked the wires they looked good. Changed the plugs and it ran fine until the engine warmed up. Any ideas?
March 4, 2010.

Engine running rough or misfiring can be cause by the following: 1. Defective spark plug.
2. Inadequate spark/coil, defective spark plug wire.
3. Lack of compression
4. False air leakage.
5. Faulty fuel injectors.
6. Insufficient fuel pressure.
7. Contaminated fuel.
8. EGR valve that is leaking.
9. Oxygen sensors.

Mar 5, 2010.