2004 RENAULT LAGUNA REVVING ON ITS OWN?

They do suffer from problems with the motorised throttle body. Sometimes it can be cleaned and reset and this will resolve the problem. Do you know if the problem is only evident when the air con is switched on? as the engine ecu automatically raises the idle speed to compensate for the air con compressor to cutting in. If the air con has low gas pressure and is not working correctly sometime the ecu will just hold the idle high as it is 'looking' for the compressor to cut in.