BMW 325e 2.7l 86 it has a big problem by the sounds of things. its reving by itself big time does sum1 have any idea what this may be also how much it will cost to change your water pump im in Au?

A hunting idle (up and down by itself) is usually due to a vacuum leak. Check all the rubber hoses going to the intake manifold for cracks or tears. If there are any torn or damaged hoses replaced them (do not try to seal them up). If your problem still persists, try removing the idle speed motor and cleaning it out with brake clean or carburetor cleaner.