Well, my suggestion would be to make sure your sources are trustworthy. If you are not sure about something ask people that know what they are talking about.
Now to your "issue": My guess would be that you found the player_burstFireCooldown dvar. When trying to change it's value you probably set the type to 4 bytes in Cheat Engine. That's gonna show you a weird value because the dvar is of type float (which might have looked like it is encrypted to you, but that's simply what happens when reinterpreting a float as an int). Try changing the type to float instead of 4 bytes.
Also, I am planning on releasing the addresses of all existent dvars in mw2 today, so keep your eyes open :)