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Identifying a Lawn Mower Engine Popping Sound and Possible Fixes

A lawn mower and a toy lawn mower.

Hearing a lawn mower engine popping sound can be startling. That noise indicates that your lawn mower is backfiring, just as similar popping sounds can signal that a car engine is backfiring. When you hear that sound, it’s important to get to the root of the problem immediately to keep your machine in working order. Here’s what to do when you hear a lawn mower engine popping sound.

What Is a Backfire?Lawn Mower

The engine in your gas mower has a combustion chamber in which controlled explosions generate power. When everything is working properly, you don’t hear these explosions, but if an explosion happens outside of the combustion chamber, you’ll hear the sound of backfiring. This indicates that the explosion is happening somewhere it shouldn’t, often in the exhaust system.

Backfires During Shut-Off

The timing of when you hear a lawn mower engine popping sound is a clue to what’s going wrong. If it happens when the engine is idling or as you’re turning it off, then you may be slowing your engine down too quickly.

Turning off your engine abruptly when you’re in the middle of mowing can cause some gas to get into your muffler. Once there, it will cause a backfire when it ignites. A good way to avoid this is to gradually slow your engine speed. Even letting the engine idle for 15 seconds before you turn it off can eliminate the backfire.

Fuel Issues

If the engine backfires while you’re in the middle of mowing, then there are a couple of possible causes. Low fuel pressure can cause a backfire when there’s too much air and not enough fuel in the combustion chamber. This can be rectified on lawn mowers with speed settings by simply increasing the speed and thus increasing the fuel supply. Another possible cause is a failing fuel pump or even an old fuel filter. If adjusting the speed on your mower doesn’t help, then look to those parts as potential problems.

Engine Issues

Another possible culprit is a problem with timing. If the spark that ignites the fuel isn’t happening at the right time, then your engine may backfire. Your engine may need a tune-up that includes changing the spark plugs. If it’s been a while since you’ve done any maintenance on your mower, make some time to give it a little attention and backfiring issues may disappear.

While not as complex as a car engine, a lawn mower engine still needs regular maintenance. Make some time to prep your lawn mower each summer and you can avoid dealing with engine backfires.

Check out all the lawn mower care products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information about lawn mower care, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photos courtesy of Flickr


Nicole Wakelin View All

Nicole Wakelin covers the automotive industry as a freelance journalist for a variety of outlets. Her work includes news pieces, podcasts, radio, written reviews, and video reviews. She can be found in The Boston Globe, CarGurus, BestRide, US News and World Report, and AAA along with lifestyle blogs like Be Car Chic, The Other PTA, and She Buys Cars. She is active on social media with a large following on both Twitter and Instagram and currently serves as Vice President of the New England Motor Press Association.

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