What causes a 4 cycle engine to surge?

The fuel tank cap has a small hole, which allows air to flow into the tank and create back-pressure to help deliver fuel to the carburetor. Dust or dirt can plug up this hole. As a result, the carburetor won’t get enough fuel, leading to surging. Surging can also occur due to water contaminating your fuel.

What causes a small 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.

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.

Why is my Briggs and Stratton 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.

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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.

Is engine surging bad?

While an engine surge doesn’t cause your car to stop working completely, it can definitely negatively impact your fuel economy. Not only that, but the amount of emissions also tends to be much higher as well. Moreover, these effects tend to stack up over time when misfires happen more and more often.

Can a bad fuel pump cause surging?

An alarming symptom of a failing fuel pump is surging.



You might be idling at a stop light. The engine’s RPMs start to rise without any accelerator action on your part.

What causes rpms to fluctuate at idle?

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.

Is it normal for RPM to fluctuate at idle?

It actually is completely normal for the engine idle speed fluctuate a small amount. Gone are the days of a mechanically adjustable idle speed screw and a mechanical cable operated throttle.

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