Jetta car will not stay running

The car will keep turning over and over then start. Once started it will idle smoothly until it seems the engine gets warm and then stall out. After stalling, will try to restart and will only crank over. Car is getting fuel, checked the fuel pump, plugs, wires, cap, rotor, coolant temp sensor, maf sensor, changed the throttle body and sensor. Also checked the catalytic converter. I have researched and found that what other people are saying with the same problem, would be a crank sensor. I would like professional advice before dumping a lot of money into parts.