If you're lucky, it will be a cheap fix. I had scenic with the same engine and the same problem. Talking about renault problems....name it, i fixed it (or was trying to
) Engine should look like this ....
and what you're looking for is MAP or mass air flow sensor looking like this
and lives (if you take a look at the first picture) under thet viper blade compartment in front of the fire wall on pic's up right. There is a rubber hose going onto the MAP sensor. It's probably rotted. Unplug it and engine will cut of. Replace it and I hope it will be ok. I hope you have this simple problem