What causes lawnmower engine to surge?

The cap on your mower’s gas tank is vented with a small hole. … Surging is also caused by water that got into the fuel. A mower left in a heavy rain or condensation on a hot summer day can choke the engine. Empty the gas tank, properly dispose of the old fuel and try a fresh batch of gasoline.

What causes a lawn mower engine 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 is my lawnmower engine surging?

The most common reason for a surging lawn mower engine is a blockage in the fuel supply, but there are other possibilities: Bad gas. Bad spark plug. Dirty / faulty carburetor.

What causes an engine to hunt and surge?

Engine hunting and surging at idle is usually caused by a fuel delivery, air leak, or governor system problem. Cleaning/overhauling the carburettor, adjustment of the governor, and/or changing the air filer may be required.

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How do I stop my lawn mower from surging?

A thin coating of engine oil on foam filters typically helps them attract dirt that could end up in your carburetor. Paper filters, however, only use their pleated medium to catch dirt and dust. An air filter is a quick fix that should be your first stop when troubleshooting a surging lawn mower.

Why does my lawn mower keep bogging down?

The most common reason why lawn mowers bog down, especially mulching mowers, is grass clippings sticking to the underside of the deck. If your mower packs in too many clippings, there’s not enough room for the clippings to cycle and the blade to keep turning. … Pull the wire on the spark plug, then flip the mower over.

Why does my lawn mower rattle?

One of the most commonly experienced noises from a lawnmower is a loud rattling sound resulting from a loose blade assembly. If the blade assembly is loose, it will move around during startup, and it will keep on rattling as the lawnmower runs.

What causes a carbureted engine to surge?

Incorrect fuel mixture adjustments and engine idling capabilities can be upset by fuel mixture adjustments and fuel vapor recovery system malfunction. The fuel system cleaner added to the fuel tank can open blocked passages in the fuel system that could be causing the surge.

What is the cause of engine surging?

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.

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Can spark plugs cause surging?

3. Surging and Lagging. Another good indication that your spark plugs are dirty or worn is if your vehicle experiences surges of speed, resulting in a jerking acceleration. These surges occur because your spark plugs are not igniting the fuel in your engine at the proper rate, resulting in an uneven speed.

Can faulty oxygen sensor cause engine surging?

Oxygen sensors are among the most interesting and important sensors on your engine. … Surging is among the many problems a failing O2 sensor can cause, but it isn’t the only one.

Why is my engine revving in park?

The idle is controlled by the idle air control valve and if it cannot keep the engine idling it will keep trying to rev the engine up to compensate. A vacuum leak, sensor that has failed, or an EGR system malfunction could potentially be the cause of the erratic engine you’re experiencing.