First of all check your throttle is properly calibrated. This is happening when your throttle is not calibrated properly.
2nd thing which joystick are you using? If you are using x-55 then check axis there are two axis assigned for throttle as x-55 has separate throttle and stick. so there will be 2 x-axis and same for other axis which they fight each other. Correct me if i am wrong.
If you have x-52 pro as i have, you must must always calibrate it before starting game. Every time you un-plug x-52 pro you must re-calibrate it. Other-wise your stick and throttle will be way too much sensitive. You will pull half of your stick/throttle and it will apply full in game this is one of the issue with the x-52 pro. It don't mean that the stick has centering issue rather it will be way too much sensitive.
I hope it will help you