Hi i got a problem !
suddenly when i start up the phantom 2 one egnine is running normally och 3 egnines is running very slow, and when i trhottle up only one egnine is running faster, any idea ?

3 motors out leads me to believe it's a software update or 're calibration of imu ,GPS compass  etc in assistant software, unlikely 3 motors have failed.

http://forum.dji.com/forum.php?m ... age%3D1&lang=en
Read the forums and look for the same symptoms.
This IMU is first as we see more and more recent "out of box setups" needing this....

Can you put a Video?

Yes, please put a video for better analysis.