2001 Plymouth Neon Error Codes P1299 & P1281

Earlier this week, my Neon's engine all of a sudden started to race when I started it, as if I had my foot on the accelerator. It would do this for several seconds, then calm down a little but still high. My car would move forward on it's own, I don't have to use the gas pedal. It goes slowly but steadily up to 45, at which time I braked. Friday, on the way home from work, the check engine light came on, the car started to jerk and there is a rattling noise under the hood. I took it to Auto Zone and they hooked up a hand held computer reader and it came back with codes of P1299 and P1281. I looked around and found somew general info on these codes. The 1299 code may refer to a vacuum leak and the 1281 indicated that coolant temp was below normal range. Can anyone here give some more detailed info, such as what part to replace or check? Thanks!