Fast idle means it gains revs up to between 2 to 3000 rpm. It's random and not self curing. A throttle blip doesn't seem to help although it can delay it?!
This is happening more and more regularly which is frustrating considering it's been to the Renault service department twice.
The first time, it had the throttle body cleaned and they carried out relearns. A month later, they swapped over accelerator pedals and checked values ... Also found a pcv/evap pipe broken and replaced it. Refitted original pedal, carried out several road tests and all ok. It was then ok for a little while but the problem soon came back.