When i am driving down the hwy at 60mph and in 5th gea it will cut off. If im slowng down in neutral it will cut off. It idols low in a stopped position. And it rattles. And sometimes when im driving the rpms will go down and will acg like it wats to cut off but does not. Any suggestions?

Ok if you are runing on the fwy and let go the gas pedal the only air is coming in from the idle valve and on neutral the same ting what about wen you start the car first the rpm is high 1400 or 1500 then going down wen it get hot that car had two valves the cold idle valve and electric valve the electric valve control the regular idle wen the car is hot after the cold valve is closed