The throttle on my C172 will not engage properly on initial takeoff. It runs up to approx. 30knts then disengages. When I use the AI for initial takeoff then switch over to manual throttle all is well for touch and go landings etc. Am also having this problem with the King Air.
C152 works perfectly as does the Citation. any thoughts on this would be appreciated!
had the same issue, turn off all assisted piloting, now works fine. also make sure your throttle joystick is set to default. I contacted MSFS support and they were very helpful.
Thank You! Now works fine without the assists. 
At full throttle for take off, the engine(s) respond mininally bringing the aircraft to a slow speed of about 20-30 knots. Cannot take off. Tried this in Cessna CJ4 and 172 G1000. Prior to yesterday this was not a problem. Also, yesterday, I was not able to access MSFS but overcame that by logging in and out of XBOX. On the way to doing that I had to change my password. I have removed all AI assistance. Any and all help is appreciated.