Hi guys! My 96 silverado has started having problems this week. When I stop at a light or a sign the idle gets down around 500 rpm and the truck starts to shake. It won't choke down when you get on the gas but it won't immediatley take off like normal either, and after it goes from a stop it i fine, there is no problem as long as you aren't on the brakes at a stop. When I shift to neutral it smooths out but if i shift to reverse it is just as bad, and in park it is sometimes shakey and at low rpm. The truck had done this once before for about 30 minutes every time I would stop but I thought nothing of it since it stopped. Its at 115,000 miles by the way. Any thoughts on a diagnosis and solutions to this problem? if you need anymore explanation just ask.