Runs fine, but showing code P1300

It's driving me nuts. Car runs fine, used to stumble and shut off now and then, seemingly as it warmed up, but after waiting five to ten minutes it would start up and run fine all day long, yet showing 'check engine' light. It has been running fine for a while now, but I still have a P1300 code and 'check engine light' showing. I've replaced coil, plugs, rotor and cap. Wish there was a way or a reader that could tell me more than 'primary ignition system'.