Why is my truck cutting off?

I have 92 toyota pickup 2.2re 5speed. My truck cranks and idols fine , you can even drive it and runs fine but once you get going and your coming to a stop or like your slowing down to park it starts idling rough and shuts of. Turn the key it cranks right back up and you can take off again . this is not a very big truck or motor and there isn't but so much it could be, any advice or ideeas are greatly appreciated. Thanks in advance