Hey guys I have a 1981 Nissan 280zx Turbo and it will start up, but when it idles it goes from 1000 rpm to 500 rpm and then back up again it runs for about 5 minutes then it just shuts off. If I try to put the car in drive I can go about 500 feet before the car just shuts off. I will then try to crank it over and nothing will happen I have to let it sit for about 10 minutes before it will start back up. Any suggestions what the heck could be the problem.