Default Cpu changes maximum frequency.

Hi!

I have a D802 with cyanogenmod 10.2 .Everything is perfect except the cpu controlling. My problem is that when i set a maximum cpu frequency it wont stay there. After a couple of minute the phone override it and change it self.. I have tried setCPU , cpu adjuster and the system default settings. Do you have any suggestion. I would like to underclock my cpu because it generates lot of heat while on heavy load.
Thanks for your aswers!
Sincery,
Moqs