I purchased a 53 plate Megane last month. There are a couple of issues with it. When I start it up it dies right away, until i give it some revs otherwise it will continue to cut out. When it idles cold it holds 1000rpm, after about 10 seconds the rpm needle drops to around 800rpm and jumps up and down, the engine idles poorly juddering slightly, the engine noise is slightly tinny and I'm sure i can hear hissing at the rear f the engine which is where the throttle body etc is. Not sure if this is just the air being sucked into the throttle or a leak.

I have replaced coils, plugs, TDC sensor, coolant temp sensor and cleaned the electronic throttle body twice and even ran some Cataclean through the fuel but have not managed to resolve the problem. My code scanner has found no codes in the ECU and therefore I have no idea where else to look. My only thought was the throttle body O rings may not be tight enough and there could be an air leak? There are no other air hoses that would cause this issue and there is no idle control valve on the throttle body as it's electric.

Otherwise the car drives fine, albeit slight lack of power under load

If anyone has any experience with this problem I would love to hear from you.

Thanks