Hi scotty

I have a 2004 Renault Megane Scenic II. I know it’s horrible but anyway, when I start it cold the engine revs then dies. Then when I try again it starts. I don’t have this problem when the engine is warm. Any idea what it could be? Thanks

Hi Scotty. I have now tried this with no luck! I’m also getting really poor mpg on short journeys. Do you think replacing coolant temp sensor would make a difference?