Hyundai Repair: 2001 Elantra, Fuel filter, and Sputtering, hyundai elantra, elantra

Question
I have a 2001 Hyundai Elantra and the check engine light has been on and stayed on even after i had reset it by unplugging the battery.  Also when i start to drive, and when i am going at a constant speed i can feel the car giving too much power and then not giving enough and it feels like it is sputtering, and also at the times when i can feel this my check engine light starts to blink. Also sometimes when i am at a stop light my rpms will just start to rise, to about 3000, and when they do eventually go down it will stop at 1500 rpms for a second before going to 500-800 rpms.  I hope that you can help thank you.  

Answer
If your check engine lamp is flashing, you've at least got a misfire issue.  You should check your spark plugs, plug wires, and ignition coil for proper operation.

Additionally, you should check to see what the diagnostic trouble codes are.  As you've learned, if you turn out the lamp without correcting the issue, it'll simply come back.  The trouble codes will indicate the misfiring cylinder as well as whether the ECM detects any other issues.