Question: Why does my lawn mower keep rev up and down?

A carburetor that’s incorrectly adjusted is a common cause of poor engine idling that results in hunting and surging. Fortunately, most lawnmowers have two screws that allow you to adjust the carburetor yourself. One screw controls the idle speed while the other adjusts the idle mixture.

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. … Like other small engines, mowers rely on a precise volume of gasoline and air for smooth operations. If either of these is exceedingly rich or lean, surging may result.

Why is my lawnmower sputtering?

Clogged or Dirty Air Filters

It is one of the most common problems that cause lawnmowers to sputter. The mowers take the air from the surrounding through air filters and mix it with fuel inside the engine. So, if the air filter is clogged or dirty, it will affect the flow of air into the carburetor.

What does engine surging mean?

Engine surging is when an engine starts easily and accelerates smoothly, however after a few minutes at a steady speed, it either surges in speed or misfires. Misfiring happens when one of the cylinders of an engine’s combustion cycle fails.

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Can bad spark plugs cause engine 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 lawn mower chugging?

Clogged or Dirty Air Filters

Dirty air filters are one of the most common reasons lawn mowers sputter. Dirt can be present in the apertures that lead from the carburetor and the fuel filter and interrupt the flow of fuel supply to the combustion chamber. You want to be sure to clean or replace dirty air filters.

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.

Why is my lawn mower misfiring?

A worn, dirty, oily, or improperly gapped spark plug can cause a weak spark, and this can lead to a misfire. A quick way to check that the spark plug is functioning properly is to carefully remove the spark plug wire while the engine is running. If you hear a drop in the engine rpm, then the cylinder is fine.

Why is my lawn mower smoking and sputtering?

Leaking oil from the exhaust is the usual cause of blue, white or black smoke from a lawn mower. … Perhaps the most startling one happens when you pull the cord and the engine sputters into action, only to be followed by clouds of billowing smoke from the motor and under the mower deck.

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How do I know if my lawnmower spark plug is bad?

The spark plug in a lawn mower could be bad if:

  1. You can’t get the engine to fire up at all.
  2. You have to tug extra hard for longer than usual on the rewind.
  3. Your lawn mower loses power while moving.
  4. The gas runs out quicker than it used to.

How do I know if my lawnmower coil is bad?

One of the symptoms of a bad lawn mower ignition coil appears when you are mowing the lawn and the mower gets hot and literally shuts off. The mower must cool down over a period of time and will start and run for awhile until it gets hot again, at which time it will shut off again.