My car is idling rough, spark plugs are black and sooty, after running for a while car cuts off, then it is hard to start and when it does start i have keep giving it gas to keep it running and at times will not rev pass 3,000 rpms. Also the water in the radiator reservoir begins boilling, and when you rev the engine water shots out the radiator if the cap is off and the exhaust is blowing thin grayish white smoke. I change the thermostat and put a new distributor new wires, spark plugs, and cap.