2001 Nissan Altima Question: RPM vibration during car stop only

Without being able to drive the car and experience the problem first hand it is difficult to guess. It could be a simple a worn spark plugs but a vacuum leak, or excess fuel,(leaking injector, pressure regulator problem) could be some of the many possible problems. Your car has On board diagnostics, a scan tool would allow key sensors to be monitored straight from the screen of the scan tool with out having to do intrusive individual testing of each key engine sensor. The computer on your car looks at many sensors make decisions and then controls fuel and ignition controls.

when i stop for example for one minutes or less in the traffic light the rpm come slow and vibrated up and down so i put my left foot on the brake and right foot on the accelater pad in order to increas the rpm to level 1 but during normal drive its become normal,i got many reasons for this problem ,what is your answer please.thank you.