I'm gonna start from the beggining from were it all starterd.about a few months ago my turn off randomly. i couln't find the problem till i fount out that ignition system(xr 7000) was bad so i replaced it and it ran good. so about a month ago i did a tune up oil, spark plugs, filter. and the day after car started miss firing and the exhaust smelled like gas. the car turns on well but after a few seconds the RPM drops to ZERO while the car is still on, soon after it dies. i had many suggedtion like flowmeter, sparkplugs,timing, computer. i'm really comfused can anybody help me. by the way its a 78 280z.

Your car is nearly 30 years old, which plays a major role with a fuel injection and electronic ignition system. What I mean by this is that any one of many electrical connections could be at fault. These may lead to intermittent problems. You should begin with a general inspection of all components and connectors. Generally, it is not something like an ecu, but rather, might be as simple as a ground.

To start with, check the main ground near the battery (clean it really well and reattach), find any grounds for the ignition system and clean them, check the contacts at your coil and clean them, etc. Also, carefully inspect the harness. If it has rubbed through somewhere, and is shorting to ground, that will cause a problem too.

A good handheld voltmeter can be helpful. For example, you can check the voltage at the coil to see if you really are getting 12 V.

Sorry its not the silver bullet you are looking for, but it can be a real hassle to track this stuff down.

Good luck!