Honda Repair: What about a Honda Civic?, proper diagnosis, auto zone

Question
I recently went to auto zone to see why my check engine light was on and to fix a major problem with my car, when its in park the rpms i think it is will jump off an on between 1 and 2 and when im driving and let go of the gas to slow down a little or just keep my speed it will jerk back and when i put back on the gas it will jerk forward. They told me that my check engine light was on because i needed to replace the speed sensor (which was over $100), so of course i didnt do a thing. so i asked them what to do next they told me to replace the fuel filter and the air filter, so i did. it didnt help. whats wrong with my car?  

Answer
Stephany:
It probably was not a bad thing to change the fuel filter and the air filter, but as you now know it is not what's wrong with your car. The diagnostic codes are good and bad, good because they tell where the problem is and bad because they do not tell what the problem is. You need to have someone diagnosis what the problem is, it could be the speed sensor or it could be something that effects the speed sensor, therefore it is not working and giving out the code. If you don't have the proper diagnosis, you could end up spending a lot more by buying parts until you find the one that is bad. I'm sure Auto Zone people did not tell you that or that they would give you your money back if the parts did not fix the problem.
Good luck.
Bill