Found the mistake.
For people with the same problem here is the correct code:
function()
local modelId = 10028
local modelIdLOD = 9967
local x,y,z = -1636.3047, 682.7656, 27.4531
removeWorldModel( modelId, 1000, x,y,z ) -- Hide original
removeWorldModel ( modelIdLOD, 1000, x,y,z ) -- Hide LOD
col = engineLoadCOL( "sfpd.col" )
txd = engineLoadTXD( "sfpd.txd" )
dff = engineLoadDFF( "sfpd.dff", 0 )
engineReplaceCOL( col, modelId )
engineImportTXD( txd, modelId )
engineReplaceModel( dff, modelId )
obj = createObject( modelId, x,y,z, 0, 0, 0 )
objLOD = createObject( modelIdLOD, x,y,z, 0, 0, 0, true )
setLowLODElement(obj, objLOD)
end
)