I can tell you that its the coil pack that sits on top of the engine block. Same thing happened to my friends 98 Eclipse GS, and it also happened to my 95 Dodge Avenger 420a. The coil pack needs to be replaced. Best thing I can tell you to do is to go onto Jegs.com and order an MSD Coil Pack. They are specifically made for the 420a, and a heck of a lot more reliable, and give you better throttle response. It is the coil pack though.