What causes mower to rev up and down?

What causes mower to rev up and down?

A lawnmower that hunts and surges may be experiencing something as simple as an airflow issue. If the air that the engine requires to run is blocked, especially sporadically, it can cause the engine to slow down. When the blockage moves or clears, the engine may suddenly rev up in response.

Why does my lawn mower sound like it is surging?

When a lawn mower surges, it sounds as if the engine reaches full speed, only to decelerate quickly. Typically, it doesn’t die, but the surging may repeat during the entire time the mower is in use. Like other small engines, mowers rely on a precise volume of gasoline and air for smooth operations.

Is a surging engine dangerous?

Surging and Lagging This problem is a serious safety concern because, like engine misfires, it reduces the overall amount of control that you have over your vehicle. Address surging and lagging straight away by having a mechanic inspect your spark plugs.

What would cause a surging idle?

If an engine is not getting enough fuel (this is called “running lean”), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge.

Why do my rpms fluctuate while idling?

Why does my engine’s RPM seem to fluctuate (runs rough)? Many engine performance problems can be linked to maintenance issues such as stale fuel, dirty air filter, fouled spark plug, and deteriorated oil. Engine hunting and surging at idle is usually caused by a fuel delivery, air leak, or governor system problem.

Can a dirty throttle body cause surging?

A clogged or obstructed air filter can cause surging at idle, and foreign objects can enter the filter housing at any time. Clean the throttle body or carburetor venturi(s) after replacing a severely dirty air filter. Aerosol products designed for this purpose are available at any auto parts store.