If you have checked all the other suggestions made on idle speed and still have a problem, check this. Where the throttle cable comes into the throttle spool there is an adjustable fitting. The black sheath of the cable should be secure in that fitting (shouldnt pull out). If it does get pulled out, for whatever reason, and hangs up on the fitting instead of going back in the fitting you will get an idle speed of 1500-3000 rpm. Ron #1529 #6322