Had exactly the same problem on the TT as well as quite a rough idle after the auto choke cut outand was getting a fault code saying that the N275 valve wasn't working correctly, went on a forum to ask advice and was told to remove the throttle body, completely degrease and clean it with the appropriate cleaners and refit, did all that (piece of cake) and it totally cured the problem and cleared the fault code, the throttle body was filthy and full of gunk, the fault code that was being thrown up was actually to do with a pressure reg valve, nothing to do with the throttle body but causing the code to show....if you can fit and adjust a derailleur you can remove, clean and refit a throttle body.
it did look to be an easy part to remove. may attempt this at the weekend if its in the haynes manual....:S
The reason I mentioned whether it's an ETM and throttle position and idle relearning, is that on some Nissans (I only really know about the larger engined ones, though) when you remove the throttle body, you have to remove the multi-plug to it - and once that's removed, you have to do the procedure for it to relearn the position and relearn idle.
If your Micra has a similar throttle arrangement, worth considering. I have the PDFs from the service manual for the procedure for the larger engines.
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