My 300zx still runs automatically for about 5 or ten sec's after I turn the key to the off position then stops.

The engine runs smoothes no hesitation or timing problems just has a delay of turning off right away. ????
1990 300zx non turbo automatic

 

the guy i bought my 1990 N/A from said that he had had the same thing happen on my car. for him it was an upgraded ignition that had at some point been used for remote starting. i believe he had to just find a stock ignition and put it in.