Car owners love the sound of a healthy engine. When you turn the key in your ignition, or push the start button, you would expect to hear that sweet engine purr. But if you get unusual engine sounds when you start it, or while you are driving or idling, it can be very alarming. You might have heard the term “engine knocking” before, but what does engine knocking sound like? Is that the sound you are hearing from your engine? Engine knocking sound is usually referred to as a metallic pinging or tapping noise. It is similar to the noise created by metal balls that are shaken in a tin can.
Although engines usually produce slight metalling tapping noises after start up, hearing unusually loud knocking noises can mean that there’s a problem somewhere. Engine knocking noises are usually caused by using low-octane fuel, having faulty spark plugs, carbon deposits, worn bearings, lean air/fuel mixture, bad timing, and bad knock sensors. What does engine knocking sound like and can it be fixed? Fixing this problem is pretty easy, you will just have to fix the problem that caused it such as using high octane fuel and replacing all the faulty components. In this article, we will go through each of the causes, the symptoms, and how to fix them.
What Does Engine Knocking Sound Like? – How Do You Know If Your Engine is Knocking?
You might have probably heard or read the term “engine knocking” before since mechanics and car experts usually use it, but it can be confusing since an engine can give off many unusual sounds if it is experiencing some problem. There will be some squeaking, squealing, grinding, ticking, tapping, or clicking noises. This might lead you to ask, what does engine knocking sound like?
When people say engine knocking sound, it is usually referred to a metallic pinging sound that is somewhat similar to the sound made by metal objects or balls being shaken inside a tin can. Engine knocking may also sound like a rattle that increases in pitch along with a bad vibration. It is like cranking your car’s engine over as it gives off sounds like marbles stuck in a blender. You may hear it during acceleration, when you are driving uphill, or when you are idling.
When you notice engine knocking, you just don’t ask, “what does engine knocking sound like?”, and ignore it. It is important that the moment you hear this metallic pinging or tapping sound, you should have it corrected as soon as possible. This is because engine knocking is an indication that there is something wrong somewhere inside your engine or in the combustion process. If you ignore it and pretend you didn’t hear anything, the problem can quickly escalate and become a problem that can be very expensive to fix.
So you ask, how do you know if your engine is knocking? You will know if you hear the metallic sound. You will no longer hear that sweet engine purr, but hear a repetitive pinging or tapping noise that increases and becomes faster as you step on the gas pedal. However, the noises you hear can vary depending on what caused the engine knocking.
What Does Engine Knocking Sound Like? – What Happens When a Car Engine Knocks?
What does engine knocking sound like? What happens when your car engine knocks? To better understand what happens to your car when your engine knocks, you need to understand how an engine works.
A four-cycle engine consists of moving components that are working together as each of its pistons goes through 4 movements. Whenever you turn your key in the ignition or push the start button of your car, the car battery will supply its stored energy to power the starter which will then turn the crankshaft. This crankshaft is found at the bottom of the engine, exposed to the oil so it can have access to needed lubrication.
As the crankshaft rotates, the main bearings, connecting rods, connecting rod bearings, end bushings, pistons, rings, and cylinders are being lubricated with oil. This said rotation is necessary since it is responsible for the intake, compression, combustion, and exhaust. As the crankshaft brings about the movement of the pistons, it also allows the intake and exhaust camshafts or shafts to turn.
The camshaft on the other hand, regulates when the intake or exhaust valves are open or closed. It does this by either moving the valve stem directly or by making use of valve lifters that are connected to the adjustable pushrods and rocker arm. Each of the valve stems will go through a coil spring that closes the valve every time the rocker or cam is not forcing the valve to open. Each valve shaft has an oil seal that helps keep oil from reaching into the combustion chamber. Bear in mind that all the moving parts of the engine are being lubricated with the oil in the oil pan reservoir.
So if you hear engine knocking or any unusual noises, it can be an indication that there is a problem within the engine or in the combustion process. In many cases, knocking occurs due to the bad timing of the engine. Like mentioned earlier, the engine has many moving parts that work together. This process should be smooth. If there is bad timing, then it means that the engine components are not working properly as they should. It means that the ignition does not occur as it should and this can cause engine knocking.
Engine knocking can also happen when there are some mechanical issues within the engine. It is good that you are asking, “what does engine knocking sound like?”. It’s because you have to know how to spot it so you can recognize the symptoms immediately. It is needed since different knocks can give off different sounds and you need to recognize that certain sound so you will know what caused it and how you can fix it.
What Does Engine Knocking Sound Like? – What Causes the Tapping Sound in the Engine?
We have answered the question, “what does engine knocking sound like?”, but you might want to know what causes the knocking or tapping sound in the engine. If you know what is causing the engine knocking, then you will have an idea how to fix it or prevent it from happening.
The following problems are the most common causes of engine knocking and how you can fix them.
- Low octane fuel.
If you use fuel with a lower octane value than the one recommended for your car, it can result in the fuel and air mixture igniting too early, and this can produce a detonation knock. This causes the engine knocking sound to occur.
It is important that you follow the recommended type of fuel, including the octane rating, set by your car manufacturer. Know that the higher the octane rating, the more refined the fuel, and the higher the octane percentage will be. When it is used, the detonation will be more controlled, making it less likely to ignite prematurely.
- Faulty spark plugs.
The spark plugs are responsible for creating the spark in the combustion chamber, which ignites the fuel and air mixture for the engine’s power stroke. If you have faulty spark plugs or ones with the wrong gap or spacing, it can result in an engine knock. This can happen since spark plugs have different heat tolerances and can bring about premature detonation or detonation knock. The spark will be too weak to ignite the fuel/air mixture if the gap is too narrow. But if the gap is too wide, the plug might not spark at all. This can be fixed by using the right spark plugs or replacing the faulty one.
- Carbon deposits.
Fuels that are often used today contain a cleaning agent that is capable of removing existing carbon build ups. As useful as they are, this cleaning agent can’t keep the carbon deposits from forming. This is because burned fuel will always have carbon as a byproduct. This carbon can take up the space inside the cylinder which can increase the compression amount, and this can result in the knocking sound to occur. Fortunately, you can correct this problem by applying a specialized fuel injector additive or cleaner to get rid of the carbon sludge from various engine components.
- Worn bearings.
Worn bearings can also result in rod knock. This can happen since the car’s pistons travel up and down in the engine block. These pistons then turn the crankshaft, transmitting power to the wheels, and allowing the car to move. The rod bearings assist the piston movements and when these rod bearings start to become worn, the pistons tend to knock against the crankshaft, producing engine knocking sounds. To correct the problem, you will have to install new bearings or do some repairs on the crankshaft and pistons.
- Lean air and fuel mixture.
When a spark ignites the compressed air/fuel mixture, combustion happens. However, if there is too much oxygen in the said mixture, it will become lean. It means that there is an insufficient amount of fuel in the mixture to burn quickly, and this can lead to multiple detonations and engine knocking sounds. If the problem continues, not addressing it immediately, it can result in your cylinder walls and pistons to become damaged.
This problem is caused by faulty engine components responsible for regulating or controlling the flow of both fuel and air. To fix this problem, you need to ensure that your car’s oxygen and mass airflow sensors are working properly. You also need to inspect your fuel injectors and fuel pump and check for any signs of damage or wear.
- Bad timing.
Another thing that can cause engine knocking, which can lead you to ask “what does engine knocking sound like?”, is bad timing. It means that the ignition timing is wrong. This timing is known as the particular moment when the spark plugs fire and ignite the fuel.
To optimize the efficiency of the car, the exact timing is vital and this is regulated by the car’s onboard computer. If there is bad timing and the spark plugs are not firing as they should at the exact time, it can result in uneven burning of fuel and multiple explosions in the cylinders and it causes the engine knock.
If you notice this problem, you need to have it checked immediately. If you ignore this timing problem and the engine is left knocking too much, the problem will become worse. You might damage your engine or encounter problems that need expensive repairs. You can take your car to an auto repair shop and have a professional adjust the timing for you.
- Bad knock sensors.
A bad knock sensor can also lead to engine knocking. This can happen since the knock sensor is responsible for recognizing a knocking issue on your engine, should it occur. If a faulty knock sensor fails to detect this, it will allow the engine to knock and you won’t be alerted.
Cars in this modern day are equipped with various sensors. They are responsible for making sure that everything works perfectly, from the air/fuel mixture to the timing. When these sensors have detected that there are some knocking problems, they will send this information to the car’s computer and it will adjust the air/fuel mixture by itself so you won’t have to manually adjust the timing. So when these sensors fail, engine knocking will occur.
To fix this, you will have to scan your car using an OBD II scanner tool to determine what caused it. If you have a faulty knock sensor, it needs to be replaced. Once replaced, your car should readjust the timing and the air/fuel mixture by itself. You can then clear off any fault codes and wait if a problem will show up again. If there’s none, then the problem has been fixed.
In this article, we answered the question, “what does engine knocking sound like?” and more. Hopefully you’ll do what it takes to fix the problem and stop the engine knocking. If you don’t, the problem may become worse, leaving you no choice but to deal with the very expensive repair bills or sell your damaged car as is.