Parking last night, my 1.1 eco active engine would be at idle then start revving by itself, dropping back to idle, revving again etc and the EML come on. I disconnected the battery and had a look around as well as I could in the dark. I saw the airbox had lifted partly off of the throttle body as the bolt fixing had pulled completely out of the hole it's meant to sit in. I pushed everything back into place with a view to securing the airbox securely. I reconnected the battery and fired her up and the engine runs smoothly, but the EML is still on. Any idea what could cause this?