Engine Rattles When Accelerating? Diagnose the Cause Yourself

A smooth and quiet ride is a sign of a healthy engine, however at some point you may have experienced a rattling sound after hitting the gas, good news, you are not alone, bad news? Your car maybe crying for help. This issues disturbs many people especially when you can not exactly tell where the noise is coming from and that's why we prepared this article to equip you with some knowledge to diagnose common causes of rattling in your car.

Major Causes

Loose Exhaust parts

The exhaust system directs burnt gasses from the engine after the combustion cycle. The gasses are usually under high pressure and loose bolts, brackets or broken exhaust pipes would cause parts of the system to vibrate hence creating the rattling sound. It is usually characterized by a knocking sound coming from below the car.

A thorough inspection of the exhaust system may required to help identify the loose or damaged clamps, exhaust hangers, or brackets. Tightening loose parts and replacing the faulty ones may help you solve this problem, but this is not the only cause of rattling sound, we have more causes below.

The Catalytic Converter

It is an exhaust emission control device which converts toxic exhaust gases and pollutants from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Internal debris stuck inside or a broken core may produce a rattling sound from the vibration of the exhaust gasses passing. This noise is particularly noticeable during a cold start.

Due to the complexity of the catalytic converter and the environmental regulations, dealing with this complex part is best left to professionals.

The Heat Shield

This is a very essential part in a car as it protects occupants and car parts from the heat generated by the engine and the exhaust system. They are made of materials known for their excellent heat reflection and absorption eg aluminum, stainless steel and fiber glass. A broken, damaged or loose heat shield can vibrate against the nearby parts or itself causing a rattling sound which in most cases seems to be originating from the engine bay.

Fixing this problem is simple and maybe considered a DIY as it only requires tightening loose parts or replacing the heat shield itself.

Engine Wear

Rattling sound noise from the engine itself maybe a sign of a major problem as it may be caused by:

• Failing hydraulic valve lifter: Its a part that opens and closes the engine intake and exhaust valves. Failure to have this part repaired can spread the damage to other parts like rocker arm, push rod and the valve tip. Replacing all valve lifters if one is faulty is recommended since others are likely to fail shortly after.  This is usually characterized by a deep tapping or knocking sound coming directly from the top of engine head. Professional knowledge is required to identify and replace the worn parts.
• Piston Slap: Pistons have a tight airtight fit with the cylinder wall but due to wear and tear, this gap can becomes large enough that when the piston rocks from side to side in the bore it “slaps” the side of the cylinder and causing a clacking rattle noise.

Low Oil Level

Most engine parts require oil which acts as a lubricant, to function properly and when the oil level and pressure are low, they can cause metal components and bearings to start grinding against each other producing a rattling sound.

This tapping or ticking sound is usually persistent and doesn’t dissapear when the engines gets warm.

The only long lasting and prevention solution to this is checking the oil level regurally since proper lubrication of engine parts is vital for engine health. If the noise still remains after topping up oil, it may be a sign of low oil pressure or other lubrication issues which calls for a professional engine check.

Suspension System

This is the part that connects the car wheels to the chassis of the vehicle. A good suspension systems absorbs vibrations from the wheel ensuring a smooth ride, however worn out shock absorbers, bushes, struts or even control arms may produce a rattling sound during acceleration due to vibration which becomes pronounced when driving over bumps or uneven surfaces.

A good suspension system is a necessity in every car, and worn components should replaced instantly to restore a smooth ride. While dealing with some suspension parts is DIY friendly, most of the work requires a professional technician to work on.

The Serpentine Belt

The serpentine belt is a long rubber belt that transports power to the engine accessories—the alternator, power steering pump, air conditioning compressor and (sometimes) the water pump. This belt can become worn, cracked, or stretched over time. A loose or damaged drive belt can produce rattling noise in the car when accelerating. 

A highly-pitched squeal noise when accelerating is the most common symptom of this issue.

Regularly checking the drive belt (serpentine belt) for wear is crucial. A worn drive belt should be replaced promptly to avoid more problems.

The Ignition System

When the rattling sound is followed by a decrease in engine performance, the problem maybe lying within the ignition system. Faulty spark plugs, ignition coils, or ignition timing cause engine vibrations due to which the car rattles when accelerating.

Replacing spark plugs, inspecting ignition coils and the ignition timing can solve the problem producing the noise.

Your Concerns Answered

1. Is engine rattling always a sign of alarm? While some causes of rattling are minor and easily fixed, others maybe signs and symptoms of more severe issues. It’s always best to have the problem checked instantly to avoid more potential damage.
2. How urgent should I fix a rattling noise? Addressing a rattling noise should be sooner rather than later as this can prevent minor issues from building into major ones which may call for costly repairs.
3. Can regular maintenance prevent rattling noises? Yes, many rattling noises can be prevented by regular vehicle maintenance. Keeping up with scheduled service and inspections can help identify and resolve issues before they become audible concerns.

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