Just been for a drive on a fast dual carriageway nearby, had to accelerate hard out of a lay-by to fit into fast moving traffic,when leaving at next roundabout the revs were stuck at 5000. Stopped and lifted the bonnet somewhere safe to investigate and after a good look found the problem, the rubber grommet at the engine end of the throttle cable had become detached into the throttle mechanism easy fix hope this helps if it happens to any one else
