What is the computer saying? Have you run a diagnostic test?
Well if it is saying cylinder misfire, then its two things, needs new plugs and wires, and coil pack, so test to see if ur coil packs are working. So if the test is saying for example cylinder 5 misfire, check the coil pack for cylinder 5. You know how to test the coil packs, Take off the plug wire of the coil pack one at a time, so just take of cylinder 5 wire from the coil pack and start the car if the pack is good you should be able to see the spark of the coil pack. if nothing its bad...thats a 30.00$ fix.
Hope this helps..This happen to mine.