Tractor Repair: TC29D throttle adjustment, shade tree mechanic, diesel tank

Question
My TC29D will not hold throttle setting.   It throttles down at various times.   Is there a simple adjustment within the capability of a decent shade tree mechanic?

Answer
it sounds like an injector pump problem but first change all fuel filters put a cup of engine oil in the diesel tank and run tractor preferably for at least an hour
if there is no improvement you probably need to get the pump checked
im wondering do you mean the lever wont stay put or is the lever staying put but the rev's are going down