Starts runs 15 seconds then stalls as if no fuel

Fuel pump,clogged fuel filter ect.

I'm having a problem like this right now my 2000 Nissan sentra starts but doesn't go above 500 rpms then dies. Anyone know what's causing that?

Could be a clogged converter, Run engine for 10-20 minutes and look underneath and see if the converter is turning orange.

I have this problem also, with my 370z. When cold, it runs fine, but when operating temperature is reached, it stalls every 12 seconds. I restart, runs perfect again for 12 seconds, then stalls. Over and over again. It seems like every 12 seconds, the engine is trying to compensate or adjust the idle, but fails to keep the engine running. Only rarely it's able to barely not stall, run fine for 12 seconds, then takes a dip again. I took it to two Nissan garages, nothing was found. I do have a P0430 en P0420 error, not sure if this is causing it, or the effect of something else, but I do know my catalytic convertors are fried, because of an alternative type of fuel I'm using (LPG). Could you check if your catalytic convertors are still intact? A snake-camera (or how you call it?) should be able to take a look in the exhaust system, or you could unscrew some bolts I guess, and take a look for yourself.