2002 Honda Accord RPM bounces iA range of 2750 - 3250

2002 Honda Accord Mileage: 57,000. I decided to replace my own timing belt and I just finished today. I was very careful to line up all the marks, and I was ecstatic when the car actually started after I put everything back together. But I have a check engine light that is on that doesn't remove itself with the simple negative battery cable removal trick, and the car runs great, until the motor speed gets to 3000 rpm where it bounces in a range of 2750 to 3250 rpm, independent of how much gas I apply. I have taken the valve cover gasket off to check the marks on the cam to make sure that they line up with the crank and they both look perfect. I'm pretty sure the balance shafts are correct as well, I was very careful. Could I have damaged something to cause this problem? Is the car so old that "correct/factory timing" is off and I should adjust for that? Please help if you can, this car doesn't have adjustable spark timing, as far as I know.