92 Astro van

i got a new radio for my astro and was to cheap to buy a wireing harness and all the speakers work it turns on but it gets really hot and does not save my presets i do not know if my ground is not connected well from being so old or if i got the wireing mixed up cause i hooked red up to orange and yellow up to yellow then i put a wire nut on the remaining gray and another color that i forgot. so my question is why is it not saving my presets. and why is it getting hot.