A little shake, rattle, and roll can be a good thing when you want to go out and dance to the music. However, hearing an unusual rattling noise when you accelerate at low speed can leave you worrying about a potential breakdown followed by a hefty repair bill.
If you hear a rattling sound coming from your car when it accelerates, it’s likely due to multiple factors, such as loose components in the exhaust system, clamps that aren’t secure, rust in the wheel well, or problems with the suspension system.
The good news is that many things that can cause your car to make a rattling noise as you accelerate at low speed won’t necessarily leave you stranded on the side of the road.
Though even if you let a minor case of rattling go too long, you could still be doing your car more harm than good. To help keep you from shaking down your checking account, we’re going to need to take a closer look at what can cause a car to make a rattling sound when you’re accelerating and what you can do about it.
Find Where the Rattling Sound Is Coming From
Sometimes a car making a rattling sound while you are accelerating at low speed is easy to find. Ask yourself if it’s coming from the engine bay, the undercarriage, the exhaust system, or somewhere else. If possible, try to find someone else to stand outside and listen, or have them sit in the car and rev the engine in a park while you listen.
Determining if the rattling sound is happening when you’re parked or if you only hear the rattling sound when accelerating at low speed can help eliminate a series of possible causes.
If the rattle doesn’t occur when you’re in park at 2,000 RPMs, but it does when you’re accelerating at 2,000 RPMs, it can turn your attention away from the engine bay and toward the suspension and/or exhaust system.
11 Potential Causes Of The Rattling Noise When Accelerating At A Low Speed
1. A Cracked Muffler
A cracked muffler or failed muffler weld can easily cause a rattling sound when accelerating. The muffler has a metal shroud with a welded seam that helps seal it.
Road salt, exhaust system condensation, road spray, and the passage of time can cause rust on the inside and outside of the muffler. Sometimes the seam starts to fail and will shake when the exhaust is rapidly forced through it when accelerating, causing your car to rattle.
I had this problem in an older truck of mine, that started out as a rattle that sounded like it was from the underbody. Though it only seemed to occur right before shifting from first to second gear. I wasted a lot of hours thinking it was a transmission issue. Then I tested the noise while parked and realized the muffler was unzipping itself at its rusted seam!
How to Fix a Cracked or Rusted Muffler
If you catch it early, a professional muffler shop might be able to repair the weld or patch the damaged area. Though if it’s significantly rusted, and/or other parts of the exhaust system are on the verge of failure you might be looking at a complete replacement.
2. Loose Exhaust System Components
When a car produces a rattling sound during low-speed acceleration, loose exhaust system components, like hangers and clamps, are a frequent cause.
The muffler, tailpipe, and other underbody exhaust system components rely on a series of hangers and clamps to hold them in position. However, when one or more of them fails due to rust or underbody damage it can cause the exhaust system to vibrate against the frame or failed components.
Loose exhaust system components usually happens as exhaust gasses cause the loose pipes and muffler to move back and forth rhythmically, resulting in the rattling noise when you accelerate. This is a sound that you can sometimes replicate when revving the engine while parked.
How to Fix Loose Exhaust System Components
Sometimes you can replace a loose clamp or exhaust system fastener yourself for less than $50. There have certainly been droves of people who have used stove pipe wire to essentially tie up a loose section of underbody exhaust on an older car. Though these tend to be short-lived fixes. Especially if you have other rust problems that caused the loose rattling sound when accelerating.
The cost to have a professional muffler shop install new exhaust clamps and hangers can range from $100 to $275. Though you should expect them to find other areas of underbody and exhaust system rust that needs to be addressed.
3. A Catalytic Converter Problem
A rusted or clogged catalytic converter can also cause a rattling sound when accelerating at low speed, as it approaches total failure. Corrosion, built-up deposits, and damage caused by misfires in the catalytic converter can cause structural failures inside it. These compromised pieces then rattle with the strong blast of exhaust that happens as you accelerate.
How to Fix a Catalytic Converter Problem
If your car is making a rattling sound when accelerating at low speeds due to a catalytic converter problem, the damage is likely so extensive that it will need to be replaced. This is especially true if the damage was caused to recent misfire problems that released unburned fuel into the catalytic converter.
The cost to have a catalytic converter replaced ranges from $900 to $2,500.
Though a huge portion of the cost is the replacement part. If you have a slightly older vehicle, you might be able to find a replacement at a junkyard or through a salvage parts dealer for half of what you would pay for it new.
4. A Damaged or Rusted Wheel Well
A rattling sound when accelerating at low speed that seems to come from one of the four corners of the car could also be caused by severe rust in the wheel well.
In a case like this, the rattle will be non-existent when you’re in park and rev the engine. You’ll likely also notice the rattling noise when you drive over speed bumps or other road hazards that shake the chassis of the car.
How to Fix a Damaged or Rusted Wheel Well
If you catch the damage to the wheel well early, and it’s minor a mechanic might be able to patch or weld it up. Though the larger concern is that the rusted wheel well is causing the rattling sound when accelerating in tandem with a problem in the surrounding suspension system.
The cost to repair a damaged wheel well ranges from $75 to $225.
Though this rough figure is just to patch or fix the wheel well and doesn’t include any possible suspension system repairs!
5. A Suspension System Problem
If your car makes a rattling noise during acceleration at low speed, and it’s worst when you go over a speed bump or similar road hazard, it might be due to a suspension system problem. In a case like this, worn shocks can have fractures that rattle, or when the struts start leaking, causing them to jitter with suspension system travel sounding like a rattle.
A suspension system problem will be dead silent if you rev the engine in park. Though you might be able to physically shake the parked car to create a little rattling or grinding sound.
How to Fix a Suspension System Problem
Suspension system problems that cause rattling noises rarely can be repaired by a DIY mechanic. You usually need to completely replace the failed component. Even if the failed component is only on one side of the vehicle, you’ll still likely need to replace the other side as well.
Generally, suspension system components in the front have half the lifespan of the back axle’s suspension. Though you shouldn’t be surprised if you need to replace all four.
The cost to replace the shocks and/or struts ranges from $375 to $550 per axle.
6. A System Steering Problem
Suspension system problems can also lead to steering issues, resulting in a rattling noise while accelerating. And it’s more pronounced at low speeds and will usually occur in conjunction with the steering wheel feeling loose with a lot of play or overly tight when cornering.
Suspension system problems can also lead to steering issues, resulting in a rattling noise while you accelerate.
A lot of times the suspension system needs to be repaired and the steering system needs a bushing replaced or other repairs. You shouldn’t be surprised if you also have a bad CV boot or CV joint.
This is another problem that won’t occur if you rev the engine in park.
How to Fix a Steering System Problem
This is another time when you need to turn to the professionals to repair a steering problem that causes rattling when accelerating at low speed.
The cost to have a mechanic repair a steering rattle problem can vary widely from $175 to as much as $600. The extent of the problem and any issue with the CV joint will be the heaviest factors that affect the repair cost.
7. A Rusted Heat Shield
In an older vehicle’s underbody, rust can compromise the heat shield causing it to make a produce rattling as you accelerate at low speeds. The heat shield is meant to protect the underbody and interior of the car from the massive heat and fumes of the exhaust system. Rust or an underbody collision that punctures the heat shield can cause a piece of metal to shake rhythmically with the vibration of the exhaust system creating a rattle.
Since the exhaust system vibrates the most at low-speed acceleration, the sound of a failed heat shield is more pronounced at low speeds. This is a problem that might show up as a quieter rattle.
How to Fix a Damaged Heat Shield
While there are some bush fixes to essentially patch a damaged heat shield by packing automotive insulation in the affected area, the smartest thing to do is to have a mechanic weld a patch in. If the heat shield is badly rusted, they might recommend replacing it. The good news is that this is still a relatively inexpensive repair.
8. A Bad Serpentine Belt
When a rattling noise occurs during low-speed acceleration and is accompanied by a whining noise at start-up or a slapping sound at mid-range RPMs, it could indicate a bad serpentine belt. This rattling noise will sound distinct like it is coming from the engine bay.
You can usually confirm a bad serpentine belt with a cursory inspection. If the belt looks frayed, cracked, or loose or the “Teeth” on the underside feel worn you likely need to replace it.
How to Fix a Bad Serpentine Belt
A bad serpentine belt can usually be replaced by a DIY home mechanic in less than an hour. Though there’s certainly no shame in having a mechanic do it for you if you feel it’s out of your depth or you’re short on time. You might want to also consider having a mechanic repair if you suspect there’s a problem with the tensioner arm.
9. Ticking Lifters
Lifters that don’t continuously contact the camshaft or push rod can make a strange rattling sound when you accelerate at low speeds.
Though this is usually an issue that starts out with low-speed acceleration and then worsens to be noticeable even when the car is idling. Sometimes, you might even notice the ticking or rattling noise when the car is cold and then it fades as the engine warms up.
Although ticking lifters that cause rattling might not seem like a major issue at first, if left unchecked, they can result in epensive push rod damage and other engine problems.
How to Fix Ticking Lifters
If you catch it early, an oil change to a high mileage oil might be enough to stop the lifters from ticking and abate the rattling sound when accelerating. Though you shouldn’t be surprised if the noise returns eventually, which indicates the lifters need to be replaced.
The cost to have a mechanic replace ticking lifters ranges from $65 to $125 per lifter.
It’s best to replace all your lifters at one time to save on overall labor costs.
10. A Failing Oil Pump
If the engine makes a ticking or rattling sound when accelerating at low speed, it may be one of the initial signs of a failing oil pump. However, it might become less noticeable once the engine warms up.
Once the pump starts to die, the rattling or ticking sounds gets worse and becomes prevalent even at idle. Additionally, you’ll likely also notice low oil pressure on your dash gauge and the car might also start to run hot.
How to Fix a Failing Oil Pump
Fixing a failing oil pump calls for completely replacing it. This is usually something that’s beyond what a DIY mechanic can do on their own. The part itself is relatively cheap, but depending on the model it might take up to 4 hours to complete the replacement.
The cost to have a mechanic replace a failing oil pump averages between $350 to $650. Though some newer models might cost as much as $1,200.
11. Piston Slap
Piston slap which happens when the piston makes too much loose contact with the cylinder walls can also start out as a rattling noise as you accelerate at low speeds. As the rings start to fail, the noise is likely to worsen over time. Although you might be able to drive the car for a while, but the engine damage will only get worse and the rattle will only get louder before failure.
The Cost to Fix Piston Slap
If you catch it very early, your lucking piston slap might be fixed by simply replacing the rings. Though most of the time you’re looking at an engine rebuild, which might be more than the car is worth.
Frequently Asked Questions
Can I drive with a bad heat shield?
If you can live with the rattling sound when accelerating the car should drive down the road just fine with a bad or rusted heat shield. However, you’re putting the interior of the car at risk for heat damage and or fire. If you have an exhaust leak anywhere in the car, a bad heat shield can also put you at risk of carbon monoxide poisoning. So, it’s best to get it fixed as soon as possible.
Can Rattling Be Caused By Interior Panels
One of the more annoying causes of rattling noise when accelerating is loose panels or interior components. Often a plastic retainer or clip comes loose and vibrates with the engine at a certain cadence, which might coincide with the RPMs at low-speed acceleration. Once you find the loose panel or component, you might have to replace the clip or epoxy it back into the correct place.
A lot of the reasons why a car makes a rattling sound when accelerating are linked to exhaust system or suspension problems. If you’re lucky it’s just a loose hanger, a minor muffler crack, or a rusted section of the heat shield. These problems can typically be fixed cheaply, and the car isn’t at severe risk of mechanical failure.
Wheel well rust, suspension issues, and steering problems can also cause a rattling sound when accelerating. These noises won’t occur if you rev the engine in park, and will be worse if you drive over a speed bump. Usually, when you have a problem with one, such as severe wheel well rust, you end up having a problem with the suspension system and/or steering system.
More serious reasons why your car is making a rattling sound when accelerating at low speed can include a failing oil pump, ticking lifters, or even piston slap. These are much more expensive repairs that might not be worth it for an older vehicle.
Jason Farrell is a certified master technician, the editor of Mechanic’s Diary in Pittsburgh, Pennsylvania. He is ASE (Automotive Service Excellence) certified and earned a Bachelor’s Degree in Automotive Technology from Pittsburg State University. With nearly 18 prior years of experience in the automotive field, he has extensive knowledge about Domestic, European, and other foreign makes and models of cars and light trucks. Jason’s experience working as a technician and service manager at dealerships, gave him the experience and know-how of most aspects of inspection, diagnosis, and repair from engine and drivability to electrical, HVAC, brakes, steering and suspension and everything in between.