Engine Rattle When Idle? Causes & How to Fix

The engine is literally the heart of the car and any abnormal noise that comes from it can be really unsettling as this may be a sign that the engine could pack up if nothing is done.

No car owner ever looks forward to changing their engine. The cost of an engine itself and the labor required range from $5,000 to as high as $20,000 depending on the type of vehicle. Ignoring noise from your engine could mean incurring these costs in the long run.

There are different forms of noise that can come from an engine. Some of them include knocking and rattling. In this post, I’ll be explaining some of the reasons for an engine rattle when idle. I’ll also take you through some effective ways to fix this problem from my personal experience.

Let’s dive right into it!

engine rattle when idle

Reasons for Engine Rattle When Idle

1. Defective Engine Bearings

When an engine rattles when idling, the most common cause is a problem with engine bearings. Engine bearings are made of steel and rubber, and they’re located at the top and bottom of your engine block. When these parts wear down, it causes them to make noise as you drive.

A few things can cause damage to these bearings – overloading your car (driving on rough roads or carrying too much weight), driving in hot weather conditions (engine overheating), or failing to change your oil regularly (this makes old oil more viscous).

If you suspect that your bearing is worn out, it’s time to replace it. But how do you go about replacing an engine bearing?

Once the old bearing has been removed, simply install its replacement in reverse order: first, install new oil seals and then press in new bearings into place with an appropriate tool.

Make sure everything lines up properly before tightening the bolts down firmly until they are snug but not overly tight; this could damage them or cause them to strip out over time.

2. Catalytic Converter Problems

A catalytic converter is a device that converts toxic gases into less harmful ones. If the catalytic converter is not functioning properly, it can cause an engine rattle and an engine malfunction. This occurs when the cat fails to operate properly and does not produce enough heat to turn harmful emissions into harmless ones.

The problem usually manifests itself in a rattling sound from under the hood when your car is idling, which you may or may not be able to hear depending on how close you are to it (and how loud).

If you suspect that this might be happening with your vehicle, take it back to where you bought it and have them look at it for any possible causes of this issue.

If the problem is a rattle, you may have a catalytic converter that’s become cracked or broken. If this happens, you’ll need to replace it. Most people choose to replace the entire muffler and catalyst together since they’re built into one unit these days.

3. Collapsed Lifters

Lifters are hydraulic cylinders that push the camshaft up and down to open and close the valves in your engine. When a lifter fails, it can make a rattling noise as it rotates with the camshaft. It can also leak oil from where it connects to the engine block.

There are two ways to fix this problem: replace all of your lifters with new ones or rebuild them yourself by replacing only their worn-out components (pistons and seals).

Both procedures have advantages over each other; rebuilding is cheaper than buying new parts but can be more time-consuming and messy, while replacement items will work better right away but cost more money upfront.

4. Torque Converter Turned Old

The torque converter is a mechanical device that connects the engine to the transmission. It’s used to increase the torque of an engine, by converting some of its power into rotational energy before it reaches the transmission.

The torque converter is filled with oil and cooled by coolant from an engine’s radiator. As this oil ages and breaks down, it can start making noise when you step on your car’s accelerator at idle—the spinning motion in this part of your car makes noise as well!

If you find out that the torque converter is the problem, replace it as soon as possible to prevent further damage.

5. Low Engine Oil

Your engine is the heart of your car, and it needs a steady supply of clean, fresh oil to keep it running smoothly. The oil lubricates all the moving parts within your engine so they don’t grind against each other and cause damage.

If you don’t have enough oil in your car’s system, you run the risk of damaging those parts as well as causing internal friction that can lead to heat build-up eventually leading to engine failure.

Low engine oil levels are easy to detect with an inexpensive dipstick attached to the side of your car’s hood. The first thing to do is check the engine oil level, if it is low then you might have to top it up. Remove the dipstick and wipe it clean, then insert it back in.

Pull out the dipstick again, wipe it clean, and inspect it for any signs of contamination. If you see any kind of material on the dipstick, such as dirt or sludge, you may need to change your engine oil.

Read: 16 Valve Engine

6. Defective Spark Plugs

If you have an engine rattle, one of the most likely causes is a faulty spark plug. Spark plugs can wear out and misfire, causing excessive vibration and noise.

To test the condition of your spark plugs, you’ll need a multimeter. If any of your spark plug wires are visibly worn or frayed, replace them as well—this can cause an additional problem -overheating in other parts of your car which may lead to further damage.

A good way to tell if an old or worn-out plug needs replacing is by looking at its condition: if it’s burned out or cracked around the center electrode where it touches the cylinder head when installed then you’ll need new ones.

When replacing your spark plugs, make sure that you get the correct type of plug for your car. Your vehicle’s owner manual should list what type of spark plug and/or ignition coil you should use for your car’s engine.

7. Broken Exhaust Gasket

If you hear a rattling noise when your car is idling, it’s possible that the exhaust gasket has broken. The exhaust manifold is a metal part that connects the engine to the muffler, and it’s covered by a metal gasket.

The exhaust gasket is the seal between the engine and the exhaust pipe, so if it’s broken, carbon monoxide can leak into the cabin and cause health problems for you and your passengers.

A broken exhaust gasket can also cause a loss of power at high speeds as well as make an engine run hotter than normal because there aren’t enough coolants circulating through it. The best thing to do if you suspect that this might be happening is to replace the broken exhaust gasket. You can buy replacement gaskets for as little as $100 or so at your local auto parts store or online.

To replace this gasket, you’ll need to remove it from both sides of the vehicle. It may be stuck on with some old sealant. If so, use a screwdriver to pry away any residue and then wipe down both sides with rubbing alcohol before reattaching new ones with new sealant.

8. Bad Piston Rings

The piston rings are what seal the combustion chamber in your engine. If they are worn out, they will cause a rattle at idle. You can replace the piston rings yourself and have them fitted to your engine by a professional mechanic if you’d like to save money on labor costs.

The easiest way to determine if your piston rings are bad is by checking their thickness using calipers or micrometers (the tools used for measuring small objects). If they’re worn down below 0.20 inches, they’ve probably been damaged beyond repair and should be replaced immediately.

9. Engine Heatshield Coming Loose

The engine heatshield is a piece of metal that surrounds the engine and is connected to the body by a bolt. When this bolt loosens, it can cause an issue with your vehicle’s idle.

If you notice an engine rattle when idling, check to see if the heatshield is loose. The first thing to do is tighten this bolt down with a ratchet and socket wrench set. If this doesn’t solve your problem, then you’ll need to replace your heatshield altogether.

Read: Car Window Squeaks


If the noise is getting worse, you should have it checked out. The engine rattle when idle may be caused by a number of things including the engine heatshield coming loose, bad piston rings, defective spark plugs, low engine oil, torque converter turned old, collapsed lifters, catalytic converter problems, defective engine bearings or broken exhaust gaskets. If left untreated, these problems can end up costing you a lot of money.