Nissan Repair: 300zx rebuild, 300zx, rpm

Question
I have a 300zx with and we can start the engine and runs great.  When you turn the ignition switch off.  The engine keeps running.  

Any ideas.

Answer
Hi Jesse -

I need more information -

What year is your car? When it runs after you turn the key off, how long does it run for? Does it run smooth or erratic?

What is the RPM at idle? Could be that the idle is too high, causing afterrun

Let me know
calvin