Damaged Piston

Engine Knocking – What It Means & How To fix It

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A good car engine should run smoothly with little noise.

However, if your car produces rattling, ticking, or knocking sound, it could be a sign of engine trouble.

Engine knocking is produced when the car’s fuel burns unevenly. Instead of proper combustion, you have a lot of unburnt fuel. If you hear a ticking sound, the problem could be a lack of lubrication in the combustion chamber.

You could also have a detonation, which means that the fuel is burned too early, causing the combustion to push the piston down before it has even reached the top. This can be very dangerous for your engine and should be fixed as soon as possible.

Car Engine Knock Causes

In this regard, you will need to check your engine for oil leaks. Below is a list of possible causes for engine knocking.

1. High carbon deposits

Car Engine Repair

Unburnt fuel will lead to high carbon deposits. Fuel has a high carbon content, which often remains after combustion. Over time, these carbon deposits increase, resulting in inefficient combustion. You can solve this problem by adding a carbon cleaner to your fuel.

2. Wrong spark plugs

Spark plugs provide the ignition spark for the ignition of the fuel-air mixture. However, if you buy the wrong type of spark plug, you will experience engine knocking. In most cases, the wrong spark plugs have a gap that is too narrow or too wide.

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In the first instance, the spark is too weak, while in the second instance, the spark plug may not be able to produce a spark at all. Ask your mechanic to recommend the right spark plugs for your car.

3. Using fuel with a low octane rating

Engine Knocking

The fuel-air ignition should occur at the right time. If you buy fuel with a low octane number, premature combustion may occur. This will cause the engine to knock. To solve the problem, always buy fuel with a higher octane rating than recommended by the manufacturer.

If you still have low octane fuel, you can add an octane booster to rectify the problem.

4. Improperly lubricated cylinders

The combustion cylinder must be properly lubricated for proper operation. If this is not done, the cylinder will knock against the walls. The main problem is that the cylinder does not receive the right amount of lubricant due to loose valves or tappets. An oil leak could also cause the cylinder head to receive less oil.

5. Unbalanced air/fuel mixture

The correct amount of air-fuel mixture is necessary for the engine to function smoothly. Too much fuel will lead to uneven combustion. This leads to further damage to the piston and cylinder walls. You are then forced to replace them immediately or risk further destroying your engine. Check your injector sensors for dirt accumulation.

6. Wrong Ignition timing

If you have an older car with an adjustable distributor, it is possible that the ignition timing is too far advanced, which can lead to detonation.

How to Fix Engine Knocking

Getting the right fuel

If fuel has a high octane number, it burns rather slowly, while low octane fuel burns faster. High-performance cars such as sports cars use high octane fuel, while normal cars tend to use low octane fuel.

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If you have a car with a carburetor, then fuel efficiency is reduced and you may be forced to try some high octane gases. Modern cars have the latest fuel injection technologies, so no fuel adjustments are necessary. For most cars, the best octane rating of the fuel is 87.

Buying the right spark plugs

Cheap articles are not necessarily cheap in the long run. You can buy some cheap spark plugs in the hope of saving a few dollars only to find that they do more damage to your engine. Ask your mechanic to get you the spark plugs recommended by the manufacturer.

They often go for around 10 dollars but you will need to pay the mechanic extra for installation.

Manage boost pressure

If you have too much boost in your car, this can lead to premature detonation. In this case, you will have to modify your engine to absorb the boost pressure. If you use a turbo, it is advisable to modify your tailgate to dissipate the excess pressure.

Adjust air/fuel mixture

If your fuel injectors are not working properly, you will experience a detonation. A lean air-fuel mixture can result from leaking vacuum lines or worn seals. In this case, if the car is idling, you will notice some hesitation when accelerating. Have your mechanic check for clogged carburetor nozzles, dirty fuel injectors, or a clogged fuel filter.

Remove carbon deposits

Fuel is made from carbon molecules. These often accumulate in the combustion chambers and thus reduce the efficiency of the engine. A dirty engine has carbon deposits on the pistons, which can affect the compression of the air-fuel mixture. Too many carbon deposits lead to detonation. A chemical cleaner can be used to remove the deposits.

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Fix the knock sensors

A knock sensor is a modern innovation in many cars. It works by detecting vibrations in the combustion chambers and sending this information to the ECU. If detonation is detected, the on-board computer temporarily stops the ignition. However, over time the sensors become faulty, which means that you will not be able to control the detonation.

Keep your compression ratio reasonable

A ratio of 9.0:1 is recommended for most cars. This is not the case for cars with knock sensors, where you may have higher compression ratios. If you need a boost, you can choose lower static ratios of less than 8.0:1.

Unless you plan to use racing fuel, it is recommended that you keep compression ratios within the recommended range. You may try to use cylinder heads that contain larger combustion chambers or a head gasket shim that is made of copper.


The main cause of engine knocking is when you have a large amount of unburnt fuel. This finds its way to the engine exhaust and you will notice a smell of rotten eggs. Engine knocking can lead to further engine damage if it is not remedied immediately. To reduce engine knocking, you should ensure that you use low octane fuel. You should refer to the manufacturer’s manual to find the correct fuel for your engine.

1 thought on “ Engine Knocking – What It Means & How To fix It ”

  1. Is it possible to hear knocking sound on automatic transmission? and why is it sounding like when it had only 8400 Km on it. Trax Chevy 2019 AWD. Noticed also only makes sound when atmospheric temperature is high like above 25 deg C.

  2. If you need answers to your car questions, it is much more likely that you will get answers in our car community. You can find our community here.

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