this would be down to too much air in the mixture (its called hunting) it could mean that you have a inlet manifold leak allowing air in or the adjusting screw may need some adjustment if it is running not to much wrong prob just adjustment not sure which screw it is but once you have found it screw it all the way in and then wind it out about 1 1/2 times rule of thumb this will be ok
kev
April 2007