I recently got a trex 450 clone in a trade. Bond to the dx6i. My problem is when i push the throttle stick up, nothing happens. but when i turn the throttle hold switch off, they spin on there own. even withthe throttle stick all the way down. like the throttle switch is the power source.. its very strange to me. Im new to the 450 size.. and just got familiar with the mcpx , so baer with me lol. thanks in advance.

Seems to me that your transmitter is in idle up mode. That is the throttle curve is like a V or U, or even flat line at 100%. It is for 3D and allows you to fly upside down where the blade pitch changes, but the throttle remains high on throttle stick movement up or down.

     "Seems to me that your transmitter is in idle up mode. That is the throttle curve is like a V or U, or even flat line at 100%. It is for 3D and allows you to fly upside down where the blade pitch changes, but the throttle remains high on throttle stick movement up or down." 
If I remember the DX6I correctly it too has a flight mode switch at the top left. Perhaps the previous owner had the full throttle setting at selection 1 or 2 Flip it down to normal and see if that clears the issue. </p>

Hey mate, Check your Throttle Curve and make sure you aren't in Idle Up!