Hi. I would advise checking the wiring at the rear of the engine especially underneath the security cover on the left hand side of the injection computer, this can rub through on the cover or water can contaminate the computer/wiring. If the wiring is good, the most likely culprit is the throttle body located underneath the inlet manifold. I have changed numerous ones of these and they are not cheap unfortunately. You can try removing it and cleaning it, but this has only a small success rate, and not usually long term, but from your description as long as the wiring is ok my money is on the throttle body has got a fault. You can get Renault to take a look and check for trouble codes and monitor the potentiometer values from the throttle pedal and motor to be a little more certain, but ultimately it does usually come down to replacing it to eliminate it. The other area that can cause the revs to be this high is an air leak, but I would expect this to occur all the time, and in my experience this engine does not suffer from air leaks unless someone has carried out a previous repair and not fully sealed the manifold or injection computer. I hope this helps. Kind regards