A damaged fan blade can cause a leaf blower to vibrate excessively; replace the fan blade if it's cracked or damaged. An engine problem can also make a leaf blower vibrate too much.
Do preventive maintenance on the leaf blower to keep the engine running smoothly. If the engine still runs rough after preventive maintenance, a dirty carburetor could be causing the engine to sputter. A partially clogged jet in the carburetor may be preventing the right amount of fuel from reaching the engine cylinder. Rebuild or replace the carburetor if the engine sputters and vibrates.