Good Afternoon everyone I'm new to the forum and looking for some advice on a riding lawn mower that I'm trying to repair for a friend. It is a Chraftsman Lt 1000 it has a 16 hp Briggs and Stratton Engine on it. (Model #283H07 Type #0399E1 Code #050609ZE) The mower is several years old and has been taken care of fairly well. The following have been replaced: Air Filter, Spark Plug, Fuel Filter, and New fuel in tank with old fuel drained out. The issue I'm having is the idle just randomly starts going up and down, the only way to get it to level out when it does so is to put the choke to it. I have not been able to diagnose when and when not it will do this, it just randomly does so. I have checked the fuel cap to be sure the vent was clean. I have sprayed carb cleaner around the edges of the carb to check for an air leak, I did not find one. I also cleaned the carb bowl out and the lower portion of the carb out...Does anyone have any suggestions as to where to go next???