Why does my Briggs and Stratton engine surge?

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.

How do I stop my lawn mower from surging?

Problems in the Fuel System



Check and clean the vent. 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 lawnmower engine to surge 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.

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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Why is my mower surging at full throttle?

If your lawnmower’s engine is surging it could be a problem with the carburetor. The carburetor mixes air and fuel to the perfect ratio for combustion. There are passages and nozzles (called jets) that route the fuel through the carburetor. … When the main jet becomes blocked, the engine will stall at full throttle.

What causes an engine to surge?

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.

How do you fix a surging idle?

Turn the engine off again, and reattach the air intake duct work to the throttle body. Start the engine and rev and hold to 1,500 to 2,000 rpm until no white smoke is coming out of the exhaust pipe. Cleaning the Idle Air Speed Control Valve with aerosol throttle cleaner can often solve an idle problem.

What causes a 2 cycle engine to surge?

The most common causes of a two-stroke engine surging include lack of airflow, contaminated fuel, faulty or old spark plugs, or a maladjusted carburetor. Fixing each of these issues involves removing parts of the engine, inspecting, and possibly replacing the equipment.

What causes a Tecumseh engine to surge?

The surging is typically caused by a lean mixture of fuel to air. They call it “hunting”. The lean mixture can be caused either through a plugged fuel supply or too much air from an air leak = vacuum leak.

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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.

Why is my engine revving up and down?

If the engine can’t keep idling, it will keep trying to get the engine revved up to compensate. The cause of the erratic engine you’re experiencing could be a vacuum leak, sensor failure, or an EGR system malfunction.

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