If it is a manual transmission the clutch may be "slipping". If it is an automatic transmission it could also be an internal transmission problem. Is the Check Engine light on? If so a scan tool will be needed to retrieve codes stored in the computer of your car. The codes stored in the computer would indicate where the problem is or at least give a basic starting point to do tests. Another very likely option is it could be a restricted exhaust (blocked cat converter) or insufficient fuel pressure/delivery. A simple cheap thing to try is replacing the fuel filter on the firewall, should have push on hoses and the hose clamps if original Nisan should require a philips screw driver to open. 34 to 43 psi is the specification for the fuel pump for at idle regulated and unregulated fuel pressure, a pint of fuel should come from the fuel pump in 10 seconds of running.