Select Language

Diagnostic Center

What do I do when my lawn/garden engine runs rough or has poor idle?

Rough Idle

Your walk behind or riding power lawn mower and your garden implements, such as a garden tiller or wood chipper, all use small internal combustion engines for power and, like your vehicle, they require a little TLC to maintain their smooth running year after year. These engines are smaller and less complicated than the one in your car, truck, or SUV, but they all have the same requirements for operation—air, fuel and a spark to ignite the air/fuel mixture. The force of the air/fuel explosion pushes a piston down and rotates an output shaft to turn your mower blade, tiller blades or your wood chipping blades.   

Unlike your regular vehicle, your lawn or garden implement is not used on a regular basis and the non use or storage of the implement can lead to problems with it running properly when it comes time to use it. Even if the engine starts, it may have a rough or poor idle and not run smoothly. Before you give up and put the mower or garden tool back in the garage, there’s a few things you can do to analyze the problem and maybe correct it.


If your engine starts, but does not run smoothly, the usual culprit is air intake or fuel system related. Your lawn mower spark plug and ignition system are in order since they are keeping the engine running.  The problems could be the age of the fuel in the tank, dirt or debris in the carburetor, or an obstructed fuel tank vent. 

Another cause could be a dirty or clogged fuel filter that is restricting the amount of fuel getting to the carburetor.

What to Look For

If this is the first time you have tried to run the engine since last fall, fresh gas may be in order. Gas will go stale in as few as 30 days, especially fuel mixed with ethanol as it is in many areas. Ethanol attracts moisture over time and the moisture will dilute the gas. 

What to Do 

One solution to your problem is to take your mower or garden tool to a local small engine repair shop and let a professional mechanic have a look at it. If you would like to analyze the issue a bit, there are some things you can try to fix the problem.

Check the air filter. The job of the air filter is to remove dirt and debris from the air before it enters your engine. If the filter is doing its job, it may become clogged and not allow a sufficient amount of air into the engine for it to run smoothly, If the filter is dirty, it should be replaced.

If the fuel is old, it should be dumped into a container for proper disposal and fresh fuel should be added. Fuel additives are readily available wherever auto parts are sold and may be helpful in not only starting your engine, but in cleaning out any gum or varnish deposits in your carburetor while the engine is running.  

After adding new fuel, check the gas cap. In many small engines, the gas cap also has a vent that serves as the fuel tank ventilation. In order to work properly and supply a sufficient amount of fuel to the carburetor, the vent must be open and fee of any debris.

If none of these tips get you up and running smoothly, then it’s time to call on a professional. If your engine needs new air and fuel filters, or a new spark plug, insist on a product from a name-brand manufacturer, such as Champion. Also, make sure that whatever parts you buy are genuine, not low budget knock-offs.    


Once your mower or garden tiller is brought back to life, your home and garden will no doubt receive compliments from the whole neighborhood. 

Learn more about lawn & garden equipment maintenance products, find your part, or find where to buy your part today.

The content contained in this article is for entertainment and informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.

Related Stories

Related Parts

Champion® offers a wide variety of products for all your automotive needs.
Check them out!