Rattling Noise When Accelerating | 11 Causes & How To Fix

A rattling noise coming from your car can be a sign of serious issues that can cause costly damages. Knowing how to diagnose a rattling noise can help you quickly determine how serious the problem is. Some of the most common issues include:

• Bad Catalytic Converter
• Heat Shield
• Loose Exhaust Or Muffler
• Rod Knock
• Piston Slap
• Timing Chain
• Engine Accessories
• Bad Engine Mounts
• Loose Interior Trim
• Loose Items In Trunk
• Change In Cupholder

Today, we will show you how to diagnose a rattling noise when accelerating and break down how each of these issues sounds and how to fix them.

How To Diagnose A Rattling Noise When Accelerating

Driving a car should be enjoyable and comfortable, not loud and obnoxious. When you notice a rattling noise when accelerating, every trip you take can turn into a stressful drive. Seeing a rattling noise when accelerating is relatively easy, but diagnosing the issue can be pretty challenging, especially if no other symptoms arise at the same time. To analyze the possible causes of rattling noise when accelerating, you will need to narrow down the origin of the noise. Narrowing down the reason may be challenging since you must be driving to hear the rattling, but you can do a few things to help.

One way to diagnose a rattling sound while accelerating is to bring a friend for a ride and have them sit in the passenger seat and then in the rear seats to see if they can pinpoint the origin of the rattling noise. If you do not have a friend to help, you can try to identify the rattling source by rolling your windows down and driving down a quiet street. Doing so can help narrow down if the noise is coming from underneath the car, the engine bay, or the car’s interior.

Rattling Noises Coming From Underneath Your Vehicle

Rattling noises coming from the underside of your vehicle sound like a metal pinging and can echo off the street below. You may be able to hear these sounds through the floorboard, and you might feel a slight vibration near your feet. This sound will usually be louder with the windows down.

— #1. Bad Catalytic Converter

The first issue that causes a rattling noise underneath your vehicle is a bad catalytic converter. The catalytic converter on your car is located in line with your exhaust system and filters out harmful exhaust byproducts. Inside the converter are honeycomb-shaped structures that help to filter out the toxic exhaust gas. When these structures degrade and fall apart, they become trapped in the catalytic converter, causing a rattling noise when accelerating. In some cases, pieces of the converter can break off and shoot down through your exhaust pipe, causing even more noise. Replacing a catalytic converter can be costly, so keeping it clean with a catalytic converter cleaner can help keep it in working order.

— #2. Heat Shield Issues

Most cars have heat shields that surround various pieces of your exhaust system. These heat shields are metal shields designed to protect sensitive components of your vehicle from the extreme heat given off by your vehicle’s exhaust system. Heat shields are found on the exhaust manifolds, the underside of the car, and on various exhaust components. Over time, these heat shields can become loose, damaged, or rusted due to various road hazards. Damaged heat shields lead to a metal rattling sound as the heat shield works its way loose and comes into contact with the exhaust or body of the vehicle. A quick retightening of the heat shield can help fix this issue.

— #3. Loose Exhaust Or Muffler

Much like the heat shield, your vehicle’s exhaust or muffler can become loose over time. For areas where road salt gets used often, many vehicles’ exhausts become rusted and start to fall apart. A damaged exhaust system can make noises both when idling and when accelerating. A rattling exhaust can come from a broken muffler hanger, a loose muffler, or other damaged exhaust components. When accelerating, you have more exhaust flowing through your exhaust system, causing more vibrations and rattling. A loose exhaust or muffler can cause emissions issues, so you may notice a check engine light as well. This type of rattling noise comes from the engine bay, underneath the car, and near the vehicle’s rear, depending on where the loose component is.

Rattling Noises Coming From Your Engine Bay

With the vast number of components in your engine bay, many items can start to rattle over time — this can range from loose belt pulleys to a knocking noise from a worn connector rod or lifters. Let’s take a look at some of the more common issues that cause rattling noises from inside your engine bay.

— #1. Rod Knock

If you notice a knocking sound coming from your engine bay that increases in sound as you accelerate, you may be experiencing rod knock. Rod knock results from your connecting rod’s bearings having excessive clearance, causing them to move around and hit the crankshaft. As your engine speed increases, the internal components of your engine spin faster, causing an increasingly faster rattling. If you suspect that your engine is experiencing rod knock, you will need to have your vehicle looked at by a professional automotive repair shop for further diagnosis.

— #2. Piston Slap

Piston slap is another internal engine issue that can cause a rattling sound or knocking noise from your car’s engine bay. Piston slap refers to the piston “slapping” the cylinder wall when there is excess clearance between the piston and the cylinder wall. In a healthy engine, your pistons move up and down to spin the engine’s crankshaft — common symptoms like old age, a lack of engine oil, low fluid levels, and worn bearings can cause the piston to move back and forth slightly, causing piston slap.

— #3. Timing Chain

If you notice what sounds like a metal rattling or slapping noise coming from the front or side of your engine, your timing chain or timing belt may be to blame. Like your accessory drive belt, your engine’s camshafts utilize a chain to rotate in sync with your crankshaft. Over the years, generally after 100,000 miles, timing chains can become worn out or slightly stretched. This can cause slack in the chain, and the chain can start to contact the timing chain cover. If you think your timing chain may be to blame, have it checked out by a professional to confirm the issue.

— #4. Engine Accessories

Another source of rattling within your engine bay is the accessory drive on your engine. At the front of your engine, you will have various belt pulleys that attach to the crank, alternator, water pump, power steering pump, and A/C compressor. These pulleys can start to wear out over time, rattle, or cause your belt to slip. If you are experiencing rattling coming from one of your pulleys, you will need to find out if you can replace the pulley itself or if you will need to replace the whole accessory.

— #5. Bad Engine Mounts

Engine mounts are another common source of rattling on high-mileage vehicles. Engine mounts are metal mounts with rubber bushings with the sole purpose of absorbing vibrations created by your engine’s internal combustion process. Some motor mounts even help support the weight of your car’s engine. When this rubber degrades, your engine will start to vibrate more, especially at higher speeds. You can usually diagnose a damaged engine mount by revving your engine while parked and looking for excessive jerking of your engine. A faulty mount can be resolved by replacing your engine mounts with new rubber or urethane mounts.

Rattling Noises Coming From Your Vehicle’s Interior

Lastly, rattling noises can come from various components in your vehicle’s interior. These are usually the most straightforward issues to resolve and end up being something you can fix yourself.

— #1. Loose Interior Trim

If your interior trim in your vehicle has ever been taken out for repairs or to install aftermarket accessories, there could be a chance it was not re-installed correctly. Loose or damaged interior trim such as door panels, door scuff plates, and speaker covers can rattle during acceleration or when the vehicle reaches a certain speed. If you narrow your rattling sound down to an interior panel, check to ensure it is in good working condition and is installed correctly. You might get lucky with a simple fix to your rattling issues.

— #2. Check Your Trunk

Surprisingly, many rattling complaints end up being a loose item that someone forgot about in their trunk. If the rattling is coming from the trunk, verify that nothing is rolling around loosely. Be sure to check your spare tire compartment, as small items can fall into this compartment and rattle against the car’s metal body.

— #3. Coins In Cup Holder Or Glove Box

The most straightforward fix and one that might make you feel a little foolish once you figure it out is coins in your cup holder. You will be surprised at the amount of noise some spare change can make in your cup holder. Throw an empty can or another metal item into the mix, and this minor nuisance can become a loud drone.

Repairing A Car’s Rattling Noise

Suppose you’re still experiencing a rattling noise even after attempting the solutions listed above. In that case, you will most likely need help from a trusted mechanic to narrow down the issue. If you are experiencing rattling engine noise, you need to take your vehicle to a mechanic as soon as possible. Engine issues such as detonation, loose engine valves, worn hydraulic lifters, and poor ignition timing can cause catastrophic damage to your engine. Any unnecessary metal contact can send metal shavings into your engine oil, causing your lubrication system to act like sandpaper against sensitive areas of your engine.

 When explaining your rattling noise to your mechanic, be as detailed as possible. Let them know if you suspect it to be engine rattling, suspension rattling, interior rattling, or undercarriage rattling. This will help them better diagnose the issue and know where to look. It will also be beneficial to explain what type of noise you hear. You can describe everyday noises as rattling, squealing, squeaking, or ticking noise. By being as specific as possible, you can help speed up the repair process.

The Bottom Line

Every vehicle has many different components that can start to rattle over time. Diagnosing the cause and source of a rattling noise can be helpful if you are doing your repairs — this is also helpful if you hire a mechanic to handle the labor. Having your vehicle inspected by a certified mechanic as soon as you notice a rattling noise will drastically reduce the chances of further damage.

Frequently Asked Questions

How much does it cost to fix a rattling noise when accelerating?

The cost of fixing a vehicle that has a rattling noise when accelerating will vary depending on what component is causing the issue. For simple problems such as a worn-out tensioner, you can expect to pay around $100-$200. If your case is more extensive, like a malfunctioning torque converter or a valve train issue, you can expect to pay well over $500. The best way to get an accurate quote is to visit your local certified mechanic and have them properly diagnose the issue. They will determine what needs to be replaced and how long it will take, letting you know exactly what you will have to pay.

Can I drive a car with a rattling noise?

Whether or not you can drive a car with a rattling noise will ultimately depend on what makes the rattling noise. You should be just fine driving the car for smaller items that you know will not affect the vehicle’s driveability or cause more significant issues. If your rattling noise is concerning or is coming from the engine bay, you should stop driving the vehicle and have a professional diagnose the issue.

What happens if I don’t fix the rattling noise in my car?

If you do not repair a rattling component, it can lead to more significant issues later down the road. This can range from a heat shield falling off and blowing out a tire to an engine knock getting worse and destroying your engine. As a rule of thumb, you should always have your vehicle inspected as soon as possible after experiencing a rattling noise to ensure your vehicle is as safe as possible for yourself and other drivers on the road.