I'd tread very carefully with the jet wash idea, if you don't know what you are doing. Under bonnet fuses on Micra's are highly temperamental to water ingress, your HT leads and your dizzy not forgetting your air intake pipe. I use wonder wheels alloy wheel solution to clean my block and a little paintbrush, then a bit of WD40 on a rag to make the other bits shine. It comes up a treat. Jet washing, don't be surprised if you're running rough afterwards, it' easy to dislodge something, remember your temp sensors are on the side of the head by the dizzy too.
