ok i have a 1983 280zx non turbo and when you first start it up it runs fine but after it warms up it begins acting up. while driving the tach drops to zero and rolls until clutch engages (its a manuel) and roll starts itself while still driving down the road or sometimes won't restart at all. i have to just pull over and after about 30 min. of sitting there it will start again and run fine until it warms up once again. we have replaced the plugs, fuel filter, coil, distributor cap and rotor button. please help i need to get it running once again.