Excessive idle speed on start-up K 12 Micra?
The following reference sources imply it is possible that accelerator position sensor and throttle body stepper motor ECU fly by wire digital data communications system needs calibrating after any one of the electronic modules was momentarily disconnected by unprofessional erroneous trial and error attempts at troubleshooting?
References;
1)
http://www.noteownersclub.co.uk/forum/how-to-correct-high-revs-at-idle_topic1796.html
2)
https://www.launchtech.co.uk/common-procedure-pdf/HOW TO PERFORM IDLE AIR VOLUME LEARNING ON NISSAN.pdf
Due to its technical nature there is a dearth of uncommon free K12 technical expertise on this forum and changing parts at random is unlikely to solve the problem without calibration/ resetting.
You have not recently mentioned data trouble fault codes and any recurring oxygen sensor fault codes that merely confirm erroneous air fuel mixture possibly due to low fuel pressure, injector, throttle body and or M A F airflow sensor malfunctions or input air leaks due to perished split hoses, manifold gaskets or injector seals to name a few.
May I suggest that it would be more cost efficient to take it to a
Nissan Specialist in your area as they will know how to assess, investigate, test and diagnose the faults with only a detailed description of all the symptoms of the issues that you are experiencing with your vehicle?
May I also suggest that you
avoid Nissan main stealer dealers as they will price gouge to maximise sales commissions and their profits, potentially rendering your eleven year old vehicle beyond economic repair.
Perhaps you can reconsider the cheaper choice of ignoring the issue as the vehicle is still driveable or perhaps consider selling it on?
Search the Good Garage Guide in your area and also for Nissan Specialists in your area.
Reference: Daily Telegraph motoring correspondence good garage guide in your area.
http://www.honestjohn.co.uk/searchs/?q=Good+garage+guide
Good luck taking control sorting these issues that seem to be long outstanding in your many posts since Dec 2015?
Perhaps someone on here can come up with an alternative strategy and detail plan how to rationally resolve these idle issues more quickly and cost efficiently?