check engine light 2000 gc

6 days ago my 2000 gc check engine light came on. it went off 3 days ago and the vehicle has been running fine until today it was like it shifted into neutral and the rpm's went up and then back down to normal - this last a few seconds only. later in the day it reved again as if in neutral and the rpms went above 4 then back to normal. transmission fluid was checked and ok. it has 112,000 + miles... the check engine light is still off. any suggestions?

You can retrieve the MIL (fault) code/s by turning the ignition to on, (the digital odometer displays) then off and on 3 times in quick succession - with the last off/on cycle leaving the ignition in the ON position... then read the "P" code number displayed on the odometer.
It should be stored even though the check engine light (MIL) has turned off.
(If no codes are present, "Done" will appear.)

When you get the code post it here.