I have a Renault Clio 2002 and when started it idles at 3000rpm I have been told it could be a issues with the coolant temp sensor as it tested at -30C.
I had exactly the same problem on a Clio with similar generation. The contacts of the sensor were oxidized. It was not necessary to replace the sensor, plugging it in and out several times solved the issue. Perhaps some contact-cleaning spray could also be helpful.
Fuel injected motors have a fuel map in their ECU- quite literally an X-Y grid of ratios of fuel to air that will be fed to the engine. On one axis is throttle position, the other, engine RPM. Those two values determine A/F ratio.
In addition to this, there is a "modifier value" to the cells in the A/F ratio table that richens (adds more fuel) for different engine temperatures. So, when the engine is at -30C it adds, say, %30 more fuel per injection; at 0C, 15% more, etc. If your temperature sensor constantly says it's -30C, your vehicle will always run with the cold engine A/F ratio modifier active. That will give you high idle.