Possible air leak on the manifold or pipework. That would raise the revs.
Not sure if a dodgy alternator putting out erratic voltages would cause that? maybe.
Have you checked the belt for damage?
Run the engine & watch the belt see if it flaps around, Maybe the tensioner pulley.
Not sure if a dodgy alternator putting out erratic voltages would cause that? maybe.
Have you checked the belt for damage?
Run the engine & watch the belt see if it flaps around, Maybe the tensioner pulley.