Why Is My Car So Loud?: 12 Causes of Loud Engine Noise

If your engine sounds loud when accelerating, rattling while idle, or making funny sounds, you might wonder if you should be worried. Although these sounds could be any number of things, here are 13 common reasons behind loud engine noises:

Bent or Clogged Tailpipe

A kinked or clogged tailpipe can also be the cause of hissing in your engine, especially because it can lead to a restricted exhaust or catalytic converter failure. Your engine will grow noisy if it struggles to expel exhaust gasses. Alternatively, in the case of a bent or dislocated pipe, the noises that your exhaust creates can stack up, causing the whole exhaust system to vibrate and make noise.

Missing or Damaged Catalytic Converter

The catalytic converter helps reduce your vehicle’s harmful emissions and also plays a part in muffling engine sounds. As a result, the engine noises will be worse if the converter is damaged.

If you hear a rattling noise from the catalytic converter, it could mean that it’s close to failure. The converter has a lot of small parts inside that could break off over time. When this happens, they might rattle around inside the converter while the engine is running.

Alternatively, if the catalytic converter is missing altogether, there will be a very loud exhaust leak. This is a result of the catalytic converter being cut off from the rest of the system entirely.

Exhaust Manifold Leak

Your car’s exhaust manifold collects the harmful gases from the cylinders and feeds them to the catalytic converter. When driving with a leaking exhaust manifold, you’ll often hear a loud noise that’s loudest when you’re accelerating. This is the sound of the gases leaking out. A ticking or tapping noise upon startup is also common. In addition, you might also notice a loss of acceleration and power, reduced fuel economy, and a strong gas smell.

Bad or Clogged Muffler

If your car gets loud when accelerating and produces a hissing sound from the engine, you might have a clogged muffler. A clogged muffler can lead to a restricted exhaust, which can in turn result in loud engine noises.

Alternatively, if the noise is more of a loud rumble and your car is loud even when idling, a hole in your muffler might be to blame. Because it’s the muffler’s job to dampen the sounds from the engine, any damage to its structure will compromise its ability to quiet the noises.

Bad Spark Plugs

As part of your vehicle’s ignition system, spark plugs can cause a lot of problems if they go bad. Engine misfires and rough idling are two of these problems. Engine misfires usually produce loud pops, while rough idling causes odd sounds from your engine.

However, usually the only times that spark plugs cause rough running are when they’ve been in the engine so long that they’ve worn out. Alternatively, internal engine issues can cause the spark plugs to fail, leading to rough running. For instance, if the engine is burning oil, there will be oil building up on the spark plug prematurely.

Usually the only times that spark plugs cause rough running are when they have been in the engine so long that they are worn out or from internal engine issues causing them to fail.

–Anthony Harlin, ASE Certified Master Automobile Technician

Damaged or Worn Bearings

If you hear a deep rapping noise from your engine, it might be caused by worn or damaged rod bearings. Rod bearings keep the crankshaft and connecting rod in the engine in place as they rotate. If they’re worn or loose, they’ll make a dull, hammering noise that indicates that they’ll soon need to be replaced.

Inaccurate Mass Airflow Sensor

The mass airflow sensor measures the amount of air that enters the engine at different RPMs. In addition to the oxygen sensor, the PCM also relies on the mass airflow sensor to calculate the air-fuel ratios it needs to maintain for the engine to run smoothly. As a result, if the sensor is inaccurate, whether because of mechanical failure or a blockage, the air-fuel ratios are thrown off. Like what happens with malfunctioning oxygen sensors, this miscalculation can lead to rough idling.

Worn-Out Gaskets

As we’ve discussed, a leak in the exhaust system will often lead to loud sounds coming from the engine as various gases escape. The gaskets that seal different parts of the exhaust system can also fail, causing these leaks and subsequently the noises.

Damaged Engine Mounts

Rubber engine mounts keep your engine in place and prevent it from moving around and hitting the chassis or car frame while running. If the engine mounts are damaged, then the engine might end up shaking and banging against the frame.

The engine might also flex more than it should while on these broken mounts, leading to loud thuds when changing gears.

Collapsed Valve Lifter

Between your vehicle’s camshaft and each of its cylinder valves is a cylinder called a valve lifter. Each lifter opens and closes its corresponding cylinder valves as the camshaft moves. Worn, leaky, or dirty lifters can cause a clicking sound that quiets down as the engine’s RPMs go up.

Bad Idle Air Control Valve (IAC)

An idle air control valve manages the air needed to maintain a certain RPM when a vehicle is idling. Carbon buildups in the engine can cause malfunctions in the IAC valve, which results in higher RPMs while idling. Higher RPMs then lead to engine noise and a rough idle.

Other Worn Mechanical Engine Parts

Engines are complex machines with many different moving parts. There’s a good chance your loud engine problems can be traced to any one of these parts if they’re malfunctioning.
If you’re wondering “why does my car sound louder than usual,” the answer is probably one of the things on this list. It’s best to have a mechanic examine your vehicle for the exact cause. That way, you can have it fixed and go back to driving in peace.