2000 2.4l Sonata code po304 failed inspection

[greenman2007]

Have check engine light on ( failed NJ inspection) with PO-304 code which means cylinder 4 misfire... Been on for awhile, check engine..
changed all 4 plugs yesterday... Not sure if that is problem.. A couple of questions... How long do I have to drive car to have code reset if it was the plugs or is there a easier way to find out...
Also since I can't find a book at the auto stores on this car, What else should I look for to see what else could be wrong with the car, with this code.......
thank you...

[kennyspackers]

If the code is still active the light will remain on, when the problem is fixed the light should shut off and the code will just be stored in the ECM. That means the new plugs are not the problem, try replacing the plug wires that is the cheapest next step. IF that doesn't do it then it is your coil pack, that is what the plug wires plug into on the other end. #4 will be the one closest to the drivers side follow that wire and make sure the case isn't cracked or other obvious things. Also make sure the plug is pushed on to the coil pack all the way that could also cause the problem. Let me know how that works out for you.