We have three of the Hyster Fortis units. All three have the mazada motors in them. What the problems are is that they begin to run rough and idle up and down on their own. If we go in and put in a new injector in them the problem will go away for several days/weeks, depending on how much use they get. But then it comes back again and we have to change out the injector again to fix it. We have other different model units and none of them have these issues. All the units run the same LP fuel. Any sugestions or ideas?