Help! This car has run perfectly for ever and ever 240,000 miles. All of a sudden it will not run over 2,000 RPM'S. I replaced cap and rotor. What would you check next?

 

Your car is in limp home mode. It is caused by a malfunction of either the MAF (mass air flow meter) or the CHTS (cylinder head temp sensor). I suggest getting a nissan service manual or at least a haynes manual and trouble shoot those 2 items.