First look at display and make sure you are in P1 mode not P2 or P3 if that is ok. Go into service mode performance and P99 to reset all settings to factory default. After that go into analyzer A2 and look at accelerator either in display or access 3 to see if it moves all the way. Last check weight sensor in display to see if it changes when raising forks because if it thinks you have weight on forks it will restrict speed