Why Does My Car Sound Like A Lawn Mower?

Hearing your car sound like a lawn mower is frustrating and unnerving, especially if you are hearing it for the first time. Despite several possible causes, it is an easy and inexpensive repair.

If your car sounds like a lawn mower when idling or accelerating, you have exhaust leaks, or one or more cylinders are not firing well. Exhaust leaks could happen due to damaged gaskets or rusted or deteriorated exhaust pipes. Engine misfires can typically occur due to faulty spark plugs, lousy injectors, dead ignition coils, or spark plug wires if you own an older vehicle model.

This article will explain these factors in more detail and how to rectify the problem. Seat back and have a 5-minute read.

Why does my car sound like a lawnmower?

As mentioned, cars typically sound like lawnmowers due to exhaust leaks or engine misfiring. Typically, the sound is exhaust gas leaking out of the system or unburnt fuel being forced out of the engine through the tailpipe. Let’s see the reasons your car sounds like it’s purring.

Lousy spark plugs

Spark plugs are essential ignition system components that ignite the air-fuel mixture in the combustion chamber. If one or more of the plugs are not functioning correctly, it will cause an engine to misfire and make a loud noise like a lawn mower.

If your car starts running rough or making unusual sounds, inspect the spark plugs and see if that is the root cause of the problem. If the plugs are dirty or dead, clean them or replace them with quality ones.

Defective muffler

The primary function of the exhaust muffler is to reduce the exhaust noise produced in the combustion chamber. If the muffler fails or leaks, it’ll cause loud engine noise when accelerating. Though the noise will be there upon startup, it’ll become obvious as you accelerate the car.

Exhaust leaks

The exhaust system consists of several components that help export exhaust gases from the engine. If the exhaust gas escapes from the exhaust components without reaching the tailpipe, it’ll cause your car to sound like a go-kart. So, if you were asking, why does my car sound like a go-kart? You now know the answer.

Engine misfire

Engine misfire is one of the primary reasons a car produces a lawn mower sound. An engine can misfire due to several reasons. It could result from lousy injectors, dead spark plugs, malfunctioning MAP sensors, MAF sensors, faulty distributors, dead ignition coils, or lousy ignition wires causing incomplete combustion in the combustion chamber.

Engine misfire causes loss of power and increases emissions. It is very dangerous because it can cause your car to stall or come to a standstill when overtaking another vehicle on the highway. Of course, you know what that means. It’ll cause a fatal road accident. Hence, you should fix this problem as soon as possible before hitting the road.

Aside from causing road accidents and a lawnmower-like sound, driving with a misfiring engine will ruin your driving experience.

Damaged wheel bearing

Another reason your vehicle sounds like a lawn mower is damaged wheel bearings. Suppose you hear a whining or humming noise that increases as you accelerate; that indicates a damaged wheel bearing.

The wheel bearings allow the wheels to rotate smoothly and seamlessly. And they fail over time, causing a loud humming or whining noise like a lawn mower. However, you don’t have to accuse the wheel bearing without a proper inspection. The noise could also come from the propeller joints. Don’t worry. In the next section, I’ll explain how to diagnose and fix this problem.

Transmission problems

Have a mechanic inspect the vehicle if you hear a grinding or whining noise. It could be you have transmission problems. The transmission transfers power from the engine to the wheels to move the vehicle.

And if anything is wrong with it, it will make the car sound like a tractor or lawn mower. Don’t ignore this problem as it could drop expensive repair bills on the table if not fixed on time.

Old differential fluid

Front and rear differential axles need differential fluid to run smoothly. Also, the gearbox needs diff fluids to cool and lubricate its internal components. These fluids require changing at least every 30,000 miles.

Failing to change the fluid when due will cause your car to sound like a lawn mower. It’ll also result in causing catastrophic damages, overheating, gear breaking, and lockup. Since one of the primary functions of the diff fluid is to lubricate and cool the internal gearbox parts, not changing it when necessary will cause increased friction and eventually overheating in the gearbox and axle units.

If you were wondering why my car sounds like a race car or why my car sound like a motorcycle, you now know the possible causes. However, let’s look at how to rectify these problems in the following few paragraphs.

How do I fix my car sounds like a lawnmower.

Since several factors can cause a car to sound like a lawnmower, there are different ways of fixing it. Here are the possible ways to fix a lawn mower sound coming from your vehicle.

Fix engine misfire

Since several factors can cause an engine misfire, and it could result from one or more cylinders, it’s best to diagnose the vehicle with a scan tool. The diagnosis will narrow down the root cause of the problem or at least direct you to check one, two, or three components instead of leaving you to battle with several car components.

Here are the possible error codes the scan tool will display when you diagnose the vehicle.

The first error code, P0300, means there’s a random misfire—the last two numbers on each code show which cylinder is misfiring. For example, a P0301 means cylinder one is misfiring, and a P0312 means cylinder twelve is misfiring.

Issues like a faulty spark plug, wrong plug gap, lousy fuel injector, or defective ignition coil could cause misfiring on a particular cylinder. But a random misfiring can result from a clogged fuel filter, lousy fuel pump, MAF sensor, MAP sensor, and other possible causes. It could also mean more than one cylinder is misfiring.

Check these components and replace defective ones to resolve the lawnmower sound. But before checking for engine misfire, check for an exhaust leak in the system.

Fix Exhaust leaks

Slide underneath the vehicle and inspect the exhaust pipe. Check if there’s a leak anyway along the pipes. Pay close attention to the exhaust necks, joints, and the manifold. Check for black or deteriorated areas and examine them closely.

The leak could also come from the exhaust manifold in the engine bay, so it’s essential to check these areas as well. If the exhaust leaks from the neck, manifold, or joints, replace the gasket and apply gum before reinstalling them. If the leak is coming from the pipes, you have to clamp or weld the affected areas.

Replace defective muffler

As I explained earlier, the work of the muffler is to muffle or silence exhaust noise. If it damages, it will cause your vehicle to sound like a lawn mower. Therefore, you must inspect the exhaust muffler while checking the entire unit. Replace the muffler if it is the cause of the problem.

Check the wheel bearing.

If you are wondering why does my Jeep sound like a lawn mower only when driving? You likely have a worn-out wheel bearing. If the lawn mower sound comes from the wheel bearing, you won’t hear it when idling unless you drive the vehicle. And the noise will intensify as you increase the vehicle speed.

Lift the suspected wheel without slacking the tire to confirm if the wheel bearing is the cause. Hold the tire with your two hands on the upper and lower end of the tire and play it. The tire will wiggle if the wheel bearing is bad. Replace the damaged wheel bearing, and the noise will disappear.

Change differential oil

Differential oil helps in lubricating and cooling the gearbox and the differential axles. Though you don’t have to change the diff oil regularly like the engine oil, it needs to be changed every 30,000 miles or so, depending on the manufacturer’s recommendations. If you haven’t changed your diff fluid for over 30,000 miles, now is the right time to change it. It could be all you need to fix the problem.

Final Words

If you have been reading to this point, you’ll no longer ask, why does my car sound like a lawnmower? The common reasons your car makes a lawn mower sound are exhaust leaks and engine misfiring. Other issues like bad wheel bearings, old or low differential oil, and transmission problems could be the culprit.

I have also outlined how to address the problem. Follow the guides religiously, and you are good to go. However, contact your local mechanic or dealership if you don’t have the confidence to roll your sleeves and get your hands dirty.

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