By the sounds of it, your 4in1's speed controller for the main throttle channel is either damaged, or simply not working correctly. If you're getting full throttle regardless of stick input, then there is something wrong. It's likely the 4in1 is damaged. Walkera has lately made some changes to their 4in1's, not sure what it was, but they burn out VERY easily now. They used to be a bit more reliable. I've gone through 2 (newer) 4in1's that i've purchased for one of my other micros. The original one I got from the first Walkera helicopter I got is still going strong without any problems. Infact, i've been using it for so long I even managed to fatigue off one of the battery connectors that goes to the 4in1 PCB, I had to take the whole thing apart and resolder it . If I had to guess what happened for you, i'd say it was this;

You got your helicopter, plugged it in, and the main blades spun up, likely because of a reversed channel. As such, you grab the blades to try to stop the helicopter from taking off into the roof. However, by grabbing the blades, you also stopped the motor from spinning, causing an enoumous amperage spike to the ESC, which likely damaged your throttle ESC. This is how I damaged my first 4in1. Luckily, I simply told my seller about it, and he got Walkera to send me a new one, free of charge. A quick way to check is to just sniff the area the wires come out of the 4in1. If you smell burned electronics, you got a busted throttle ESC.


There is, of course, one other possibility for the problem. Something may have become disconected on the throttle side of your transmitter. It doesn't hurt to open up your transmitter and make sure everything is connected on the inside. Although, if your tail is responding to throttle changes (without you actually moving the helicopter) then I don't think it's your throttle channel.