One thing you can look at is the throttle settings
Go to "options and extras" and select "input" and then "input reporting"
as you press the throttle you should see where the throttle input starts and stops there has to be big range reported here
then go to "connected devices" and select the "steering wheel"
at the next screen select "advanced settings"
find the "throttle deadzone" and "throttle saturation"
the "dead zone" is where the actual input of the throttle begins I have mine set to "0"
then look at the "throttle saturation" , this defines where the throttle range ends I have mine set t0 "100'
If these are close together or the same what you are experiecing will happen
This may not be the problem , you could be having a hardware problem , but it is something to check