Each Mechanic calls parts differently. I work for Nissan The device in question is a Throttle chamber it has butterfly they cleaned and a idle air actuator on the bottom. Nissan sells separate as a AAC IAC valve. "Air conditioning air control Idle air control" Easy enough to Piwis Tester II unplug the 6 wire connector under the throttle chamber with a flash light look closely for melted connector and pin. I tell you the bad news latter. Lack of that second gear up shift wheel spin squeal. (remember when the car would really get up and go?) Most often is the air flow meter.
I can see if the voltage in data Monitor makes 4+ volts under wide open throttle or not. 3 volts is a sluggish car. OK that melted IAC plug is a result of moisture or cleaning the throttle chamber incorrectly cleaning on the car will wash carbon into the AAC IAC valve and can ruin even short out the valve ( something not taught in auto school) After the terminal becomes melted the engine control module can no porsche piwis 2 longer adjust the idle speed. Some time not very often you luck out and just replace the AAC IAC valve and relearn the idle and everything is ok. If the motor gallops idle up and down it needs Nissan help to see if the Engine control module is functioning properly and learns to idle. Fuel level problem is due to either the sending unit or the instrument cluster. Yes there is a inspection cover under the back seat Just don't attempt that job special tool may be necessary to remove the holding ring around the fuel pump sending unit assembly.