I have a 2006 Hyster Fortis H60FT unit that will crank but only run at idle rpm's. All hydraulic functions work as well. However, I have no throttle response when depressing the gas pedal, just idle RPM's. The display is showing me two service codes: 524261-2 and 522752-9. This unit has a Vortec GM 2400 (2.4L?) LPG. The customer states that they were operating the unit and when they were done, shut it off, and when they tried to use it again, it wouldn't run above idle. We checked all fluid levels. They are fine. We replaced the oil sending unit, but still nothing. All functions seem to be normal otherwise... Can anybody help me? Thanks in advance!