I have a 1983 280zx non-turbo, 5-speed. This morning it started and idled fine, I made one stop on the way to work, took it out of gear and engaged the emergency brakes and it shut off. It cranks fine but will not stay running below 1000rpm. It runs fine on the road at any speed, no problem. But when you slow down and the rpm's go below 1000, it shuts off. I have to turn the ignition switch all the way off and the back on before it will start. The fuel filter has been changed recently. Any suggestions? Maybe the coil? TPS?