I've been having to change spark plugs every 2,000 miles or more. Car starts great, runs great until it warms up and after initial accelleration from stop or slow down. Will backfire and stutter shake lack of power when accellerating from stop or slow down. Once it gets going it runs fine until I have to stop again. Does not happen with new plugs however I have to change the plugs bi weekly then. The Ignition Coil firing order is not the same as what Hyundai recommends for this vehicle. Coil has firing order 14 first side and then 32 second coil. However Hyundai states that it must be 1342. I noticed as well that the plug that is totally full of carbon after only one or two tanks of gas is the 3/4 plug. Was told by a mechanic it does not matter, this may be from another year Accent. However, logically these are from two different coils receiving and sending current or whatever to sensors and computers. RIGHT? The Car runs great after the plugs are changed. Great upon start.