i too have this problem but on my 97 accord. if the ignition switch isnt the problem perhaps u can check your alternator. i think my problem is that the idle control valve is full of carbon. When this happens the small amount of air that passes thru it is blocked and causes the car to shut off. to fix that you can remove the piece and spray carburetor cleaner in it and it should eat thru the carbon. also my friend had the same problem on his 300zx and told me he fixed it by adjusting the idle on the same piece with a flat head screw driver.