Why does my Engine Run Rough?

When an engine runs rough, it can be a sign of a number of problems – sometimes they can be long-term issues that can damage the engine, other times they can be momentary blips that aren’t a big deal. So why is your engine running rough, and what can you do to bring it back in line?

Engine cycles up and down

If your engine cycles its running speed up and down, this is likely due to an issue with the fuel flow. Fuel flow can be effected by a number of things-

  • Object in the gas tank: If something works its way into your gas tank and restricts the fuel flow into the exit hose, this will cause surges and stoppages of gas. Empty your tank and shake out anything that is causing a blockage.
  • Carburetor not feeding freely: Remove the plug from the bottom of the fuel bowl of the carburetor and see if gasoline flows freely from the tank, through the hose and float valve, into the carburetor. If it doesn’t, trace things back to find the problem.
  • Gummed-up carburetor: If none of these actions remedy the problem, take the carburetor apart and blow out all the orifices and jets. You may need to soak it in carburetor cleaner first to remove some of the build-up.

Engine Ignition Causes Sputtering

Sometimes a failure in the ignition system can cause a rough idle, something that is often traced back to the spark plug. Make sure the spark plug leads are secure, that the spark plug itself is clean, and that it is gapped correctly. Measure the gap and adjust it per specifications.

Wheezing and Lagging

If the air filter gets clogged up with dirt and debris, it will restrict the airflow to the engine, causing the engine to get choked up. Use a screwdriver to remove the filter cover and take out the old filter. If its a foam filter, you can clean it with hot water and light detergent, just make sure you allow it to dry completely before reinstalling it and running your mower. If it’s a pleated air filter, remove it and shake it out. If shaking it out doesn’t work, you will need to replace the filter entirely.

Regardless of the reasons behind it, you will need to remedy your rough, lagging mower as soon as possible. Aside from performance issues, this can be the sign of the deterioration of your carburetor, which can be a crippling problem and will lead to the need for an expensive rebuild.

About AndrewT

Written by Andrew T for LawnEq - The specialists for Lawn Mower Parts and Small Engine Parts. We offer genuine premium OEM parts for Land Pride, Toro and many more dependable brands.