1992 Chevy Truck

When you start the truck it will start but will idle up then die unless you are on the gas' when on the gas it will run rough like a cylinder is not firing. When you put it in gear it will die if you are not on the gas. When on the gas the rpm fluxuates when lightly on the gas and runs really rough unless you step on the gas harder then it will chug a few times and it will stop misfiring and run strong. After it warms up it will idle sometimes without being on the gas but idle will fluxate about 800 rpm and taking off while warm it will chug like its running on 6 or7 cyl then runs strong after on the gas pretty hard