Main causes of engine knocking noise
Engine knocking might be caused by anything from very minor maintenance mistakes to more complicated mechanical problems. It is important to identify the reason before avoiding extensive engine wear and repair.
The following are the most common reasons why an engine would begin knocking:
1. Wrong or low-quality fuel
The quality and nature of the fuel determine the combustion process. Each engine is designed to run with a certain octane rating. Using fuel with an octane rating below the engine requirement can lead to pre-ignition and cause knocking. Poor-quality fuel can contain several impurities that can interfere with optimum ignition, leading to dysfunctional explosions in the cylinder.
High-performance cars or high-compression engines are particularly prone to octane fluctuation. Regular use of the incorrect fuel can lead to not only knocking but also to long-term piston, valve, and cylinder wall damage.
2. Bad spark plugs
Bad spark plugs can also interfere with the engine's efficiency and should be maintained properly to avoid this. A routine inspection of the spark plugs is required to avert massive ignition problems and knocking sounds. Following the service schedule provided by the manufacturer is ideal in these cases.
3. Timing issues
Inefficient combustion and knocking result when the spark fires too early or too late in the compression stroke.
Mistimed engine performance can be caused by a broken timing chain or belt, a malfunctioning sensor, or a broken electronic control unit (ECU). Engine timing issues are especially hazardous because they upset the synchronisation of engine pistons and valves. If not repaired, such issues might lead to rough engine idling, a loss of power, or engine failure.
4. Carbon buildup in the engine
Carbon deposits can form on the piston heads, intake valves, and combustion chambers over time due to incomplete fuel combustion. Carbon deposits occupy available space in the air-fuel mixture, effectively increasing the compression ratio within the cylinder.
A higher compression ratio produces premature fuel detonation, which results in the knocking noise. In severe instances, the buildup may also create hot spots that preburn the fuel mixture before it is ignited by the spark plug. Cleaning the engine and adding good-quality fuel additives will reduce the carbon buildup and keep the engine in a smooth-running state.
5. Faulty knock sensor
Current vehicles have knock sensors that sense unusual vibrations or sounds made by unusual combustion. During normal functioning, the knock sensor tells the ECU to correct ignition timing and fuel injection to avoid damage.
But an improper knock sensor will not pick up such deviations, and knocking continues unabated. In certain other instances, the ECU might confuse sensor readings, causing improper adjustments and accelerating the problem. Replacing a malfunctioning knock sensor on time guarantees proper engine management and avoids possible mechanical failure.
6. Worn engine parts
Moving components such as bearings, pistons, and connecting rods deteriorate over time. Proper clearance between such moving components produces metallic tapping or knocking noises, especially under acceleration or load.
A loosely fitted connecting rod bearing, for example, makes a heavy, thudding sound with rising engine speed. Mechanical thudding is an indication of internal wear and must be inspected immediately by a professional mechanic. Failure to do so can cause the engine to fail disastrously and require expensive repairs.
Common signs of engine knocking to watch out for
Early detection of the signs of engine knocking can mean the difference between a routine tune-up and an entire engine replacement.
Symptoms will arise slowly, and knowing the symptoms makes it easier to diagnose before serious damage is incurred.
1. Tapping or pinging sound
The most apparent indication of engine knocking is a steady tapping, pinging, or rattling noise that sounds as if emanating from under the hood. This sound normally happens as you accelerate or when the engine is under maximum load. It will be metallic and rhythmic and reflect loose internal pieces or ineffectual combustion.
2. Noise gets louder when you speed up
If the knocking grows stronger or louder as acceleration occurs, then problems with combustion timing, worn bearings, or a misfire of the fuel may be the reason. In contrast to harmless engine sounds, the creation of knocking with acceleration is usually a mechanical or fuel-based issue that needs to be addressed.
Knocking will most often lead to poor engine performance as a result of an ineffective combustion process. The ECU also restricts power production as a protection measure when it detects knocking and introduces extreme dips in performance.
4. Check engine light is on
In most modern cars, the check engine light will illuminate if the knock sensor is detecting unusual vibrations or patterns of combustion. Diagnostic trouble codes (DTCs) for misfire, timing, or sensor error can more precisely determine the cause. The driver should never ignore this warning, as continued driving in the knocking state will continue to augment the damage.
5. Lower fuel mileage
Consistent engine knocking lowers fuel mileage. When the burn process happens at the incorrect time or can't combust all of the fuel, the engine will have to work harder to deliver power. This not only consumes more fuel but also generates higher stress on internal parts, which lowers overall efficiency and the life of the engine.
How to fix and prevent engine knocking
Though engine knocking scares people, all its causes can be regulated by timely servicing and good remedial measures. Fixing the root cause in time keeps the engine running smoothly and efficiently. The tips mentioned below rectify existing knocking and prevent its occurrence in the future.
1. Use the right fuel type
Always use the fuel grade recommended by the car's manufacturer. High-compression or turbocharged engines typically require higher-octane fuel so that they don't prematurely detonate. Suspected contaminated or low-grade fuel should be drained and filled with high-quality fuel. Refuelling at good stations often lessens the chances of fuel system contamination.
2. Replace spark plugs if needed
Checking the spark plugs for incorrect gapping and carbon deposits is advised. Replacing these parts at regular intervals is necessary for proper ignition in the cylinders. Using the correct type of spark plug is also a prominent factor in preventing misfires and engine knocking.
3. Clean the engine (carbon removal)
Preventive cleaning of the engine, regularly off the carbon deposit, which leads to knocking, is carried out regularly. This can be done using chemical fuel additives or through professional decarbonization, in which combustion chambers and intake valves are cleaned. Preventive maintenance precludes hot spots responsible for premature ignition.
4. Check timing settings
It is important for the ignition and valve timing to operate in harmony in order to carry out a smooth engine operation. Mechanics can check the timing with diagnostic tools and fix it accordingly. Replacing according to the routine provided by the manufacturers can prevent slippage or stretching in vehicles with timing chains or belts.
5. Repair or replace the knock sensor
If diagnostics reveal a faulty knock sensor, it’s important to replace it without delay. A working knock sensor allows the car’s ECU to detect abnormal engine vibrations and adjust the ignition timing, preventing damage and maintaining performance.
6. Regular engine checkups
Preventive maintenance is crucial for avoiding engine knocking and ensuring your vehicle runs smoothly. Simple practices like regular oil changes, fuel filter replacements, and routine tune-ups go a long way in maintaining engine health.
To stay ahead of potential issues, consider choosing ACKO Drive service centres. You can simply book a service online, and we will pick up the car from your location. Our expert technicians conduct thorough check-ups, including checking the functionality of all sensors and components. We provide a detailed diagnostic report before any repairs are made, allowing you to address minor issues before they escalate into costly repairs.
Bottom line
Engine knocking must never be overlooked. It might be due to something as trivial as low-octane fuel or dirty spark plugs, but it could also be due to something more nefarious, such as engine problems. Brought in early and fixed, it prevents damage to costly components, keeps fuel mileage high, and prevents costly repairs.
A softly purring engine is as much an indication of decent service as it is of a good, efficient, and long-lasting car. Regular servicing, careful fuel selection, and a sensitive ear for even a sound of impending doom all help keep the engine free from engine knocking.
Frequently asked questions
