Could be related partly to the "idling problems" old nissan engines encounter.

Try to clean the PCV and AAC (this can be DIY with carb cleaner if you know the part), and intake plenum of the engine. Also, the MAF (Mass Air Flow) Sensor may need cleaning with some contact cleaner. In the CASA, you can ask them to do a CONSULT readout of your engine so that it can diagnose any faulty sensor readings as well.