You didn't say what kind of engine or carb, but I would start by opening the mixture just so you can tell it is rich. Then on to the low speed adj. mentioned by cylic. If your carb has a small hole in the front, it is probably is an air bleed and there is probably a horizontal screw that will adjust the idle mixture. If there is no hole in the front, there is an adjustment on most carbs opposite the needle valve. give it a try. It sounds like your idle mixture is lean also. Adjust the idle mixture in very small increments or you will get way off and be in worse shape than you are now.