Do you hear some metal clucking sounds from the engine while accelerating? It’s nothing to be worried about, as it is a common experience for most drivers, called engine knocking (detonation).
Engine knocking occurs when some of the fuel in the cylinder detonates before the other fuel. Under normal circumstances, the spark plug initiates the fire, and all the fuel in the cylinder burns, the explosion of which is kept in control.
The spontaneous ignition of fuel and air in the cylinders is the key to engine knocking. In this article, we shall discuss in detail engine knocking while accelerating.
We shall also get to know the reasons behind it and how to prevent the engine knocking from happening, and how dangerous it is to the engine; keep reading if you care to know more about engine knocking sounds.
What Causes Engine Knocking When Accelerating?
Before we find out what causes that knocking sound, let’s first know ignition takes place in normal combustion. The engine burns the air/fuel mixture sequentially.
Meanwhile, the combustion is started by the spark plug some 10 to 40 degrees prior to TDC (top dead center). A spark across the electrodes of the plug creates a kernel of flame. This kernel increases in size and temperature.
There are various causes of a knocking noise. You may hear a knocking sound when accelerating from a stop or a knocking noise under the car when the brakes are applied. Let us look at things that may cause engine knocking sound:
#1. Too Low Octane.
Every engine is built to run on a certain number of octanes. This octane number determines how tolerant the fuel is to a rise in pressure, that is, resulting in the further the piston travels towards the spark plug and the more power output it generates.
When the octane number is low, we make several pockets of exploded air/fuel mixture before the piston reaches the maximum level of travel.
Thus, we produce a knocking sound and also reduce vehicle performance.
#2. Bad Timing.
To make the spark fire in an organized manner requires the computer distribution of the electricity from the ignition coil.
If this fails to happen, it leads to detonation, resulting in the engine knocking as we accelerate and the speed rises. In this case, the car starts but does not run.
#3. Lean Air/fuel Mixture.
If you have a lean air/fuel mixture, it means that the percentage of fuel to the air in the AFM is too low.
Faults in the engine management sensor come into play. These are the oxygen sensor, spark plugs, spark plug wires, fuel injectors, mass airflow sensor, and fuel pump.
Without enough fuel in each cylinder, the time for the mixture to burn is wrong. Thus, it explodes at the wrong time and thus produces some detonations causing the engine to knock.
#4. Bad Knock Sensor.
Modern cars with an engine knock sensor are capable of detecting some faults and sending a message to the ECU so that the problem can be solved.
Once this knock sensor malfunctions, it does not detect the knocking itself, and the ECU is unaware that there is an error to also deal with. This eventually results in engine knocking.
#5. Faulty Spark Plugs.
As we know, spark plugs are what deliver sparks to burn the air/fuel mixture, providing the needed power to run the engine.
These plugs age or get damaged and begin to give a weaker Spark. Sometimes, the problem might delay the sparks, causing the knocking sound from the engine when you accelerate.
#6. Carbon Deposits.
All fuels we use in our cars have carbon cleaners. They help keep the carbon deposits from building and clogging the cylinders.
When the carbon clogs/builds up in the cylinder, there is less room for air/fuel to reside, hence the engine knocking. We recommend that you use the FTI Carbon Cleaner Washing Kit; you can do the job yourself easily.
#7. Low Oil Level.
Another may be the lack of oil; the engine has been knocking. When the level of oil is below some level, the rod bearing between the crankshaft of the foot and the piston rod begins to develop a gap. This gap in formation gives a rattling as it is up and down.
How to Fix Engine Knocking?
Now that you know the sources of car knocking, let us learn how to fix engine knocking. These are some of the tips that will ensure that the rattling sound from your car disappears.
Hike up your octane rating to get a better quality and accurate combustion. This is one way to have the knocking sound disappear. Making the level of octane in your vehicle higher enables the ignition to be performed at an ideal time.
You can use the octane booster to increase the amount of octane if it isn’t sufficiently high.
Get a certified car scanner to take readings of all sensors while in motion, at different loads, acceleration, and speed. Compare these with the readings recommended by the manufacturer. The effect of this from the sources of car knocking is huge.
Monitor your timing and use the shop manual as a guide in timing fine-tuning of your engine.
Check on that knock sensor regularly with the car scanner to be sure it is in good working condition.
Make sure you change your plug if it gotten old or damaged. The spark plug will wear out due to age or mileage, delay the sparks, and that later causes the knocking sound.
Always us a right type of oil compatible with your engine type, age, and mileage. This must be so that internal parts don’t get damaged as a result of the wrong oil type or viscosity. Keep your engine oil changes to a strictly followed schedule. You never know what would happen.
Remove carbon buildup using engine cleaner, throttle body cleaner, and injector cleaner. Use the cleaners also to clean the oil passages and injectors (so that there is no injector pulse), cleaning the throttle body. Use the cleaners to clean the gas tank, also. The products dissolve carbon buildups, which are responsible for blocking fuel and spark the workplace.
FAQs.
Can You Drive a Car With a Knocking Engine?
Yes, you can still drive your vehicle, but you have to be extra careful while driving. Make sure to ease up the throttle and check the problem in your vehicle once you reach your destination.
What Does a Knocking Engine Sound Like?
It sounds like a pinging and a metal clucking, rapid as the vehicle accelerates. Initially, you will hear it only while accelerating. As soon as you hear the knocking sound, check for the problem and correct it before destroying the engine.
How Much Will it Cost to Fix Knocking?
Fixing a knocking engine does not cost a lot of money. Sometimes you will be required to change the spark plugs, thus adding costs.
Usually, it costs around $200. If the knocking sound still exists after changing spark plugs, the cost will go up because you will have to dismantle the engine and check the internal parts.
Will an Oil Change Stop Engine Knocking?
Ok, you needed to differentiate between the cluttering noise from the engine because of too low oil level or pressure, and the knocking sound that you hear from the combustion chambers. The knocking sound is due to the problems with the spark and fuel.
Oil change, therefore, will stop the cluttering sound from the valves in the cylinder head, and not the knocking sound.
Can Thin Oil Cause Knocking?
Old engines have tended to wear out engine bearings that are positioned between the crankshaft and piston rods.
When the engine bearings become worn out, they make a rattling sound every time the piston goes up or down. This is called crankshaft knock. Thick oil will stop these gaps and, hence, stop the sounds.
Final Words
An engine knocking while accelerating is another problem that a large number of us face along the way while driving.
The sound can be irritating to the ear, but more importantly, it can affect the engine and its internal parts. The causes of engine knocking sounds could range from bad fuel, faulty spark plugs, or a dirty combustion chamber.
The most important thing is a good diagnosis to aid the repair process. The wise thing to do when you hear an engine knocking sound on idle and even while accelerating is to seek professional advice immediately. Catching the problems in time will help protect the engine from further damage.