• Working
• Benefits
• Failure
• Replacement
• FAQs

Drivers can face several car engine problems. From lean air-fuel mixture to faulty valve timing, early detection helps reduce further issues. Did you know when an air-fuel mixture ignites prematurely, it causes knocking? If not taken care of, engine knocking can damage the head gasket and engine cylinders.

Car knock sensors detect the engine knocking and send the signals to the electronic control unit (ECU). Let’s go through the basics of knock sensors and learn about their failure and symptoms.

Understanding Knock Sensors Functions and Features

The role of car knock sensors is to detect the noise and vibrations from the vehicle engine and convert these into signals. These signals are forwarded to car computers.

The ECU adjusts the valve timing until uneven combustion stops. Moreover, the knocking sound is one of the car noises that shouldn’t be ignored. This is why knock sensors mounted on the engine cylinder block are essential in the combustion chamber.

Here’s the complete working of knock sensors in the vehicle.

Car Knock Sensors Working

Knock sensors, mounted on the engine block or cylinder head, detect the vibrations and resonances produced by the engine knock. The car computer receives the signal from the knock sensor and responds by adjusting engine parameters to eliminate or reduce the knock.

ECU responses include retarding ignition timing, adjusting the air-fuel mixture or altering other parameters to prevent knocking. Moreover, car knock sensors control ignition timing to prevent premature combustion and reduce the likelihood of knock. 

After the knock sensors send signals, the ECU adjusts the air-fuel ratio to prevent knock. A richer mixture can help cool the combustion process. Additionally, it reduces the chance of spontaneous ignition. 

Car knock sensor functions include protecting the engine from wear and tear to improve the vehicle’s performance. Let’s go through its benefits.

Car Knock Sensors Benefits

Knock sensors in the engine provide the following benefits:

• Detects and responds to engine knocking to prevent potential damage
• Improves performance by allowing real-time adjustments to ignition timing and fuel mixture
• Enhances fuel efficiency and reduces emissions through efficient combustion
• Contributes to engine longevity and reliability by minimising knocking
• Adapts to changing conditions, such as fuel quality, driving conditions and engine load

Faulty Knock Sensors: Causes and Symptoms

A failing car knock sensor can be due to several reasons. From wiring problems to sensor damage, faulty knock sensors pose various symptoms. 

Causes of Malfunctioning Knock Sensors

The following are the reasons behind a faulty knock sensor:

• Over time, knock sensors can wear out due to exposure to engine heat and vibration.
• Poor electrical connections or damaged wiring can also result in sensor malfunctions.
• When exposed to oil, coolant or other contaminants, car knock sensors can give inaccurate results.
• Physical damage to the sensor from impacts or engine repairs can render the sensor ineffective.

Symptoms of Malfunctioning Knock Sensors

When the car knock sensors fail, they can damage the engine in the long run. Also, this failure results in super knocks in the engine. Here are the symptoms of a failed engine knock sensor:

• Impacts power and acceleration due to incorrect adjustments made by the ECU to prevent knocking
• Inaccurate sensor readings lead to suboptimal fuel-air mixtures, affecting fuel efficiency
• The onboard diagnostics (OBD) scanner detects sensor issues and causes the check engine warning light to turn on
• Knock sensor problems lead to higher emissions as the engine struggles to maintain proper combustion

Other problems include the following:

• Incorrect camshaft or valve adjustments cause engine misfiring
• Knocking sounds from the engine during acceleration or under load indicate sensor failure
• Faulty knock sensors can result in the car starting roughly and then smoothing out.

Car Knock Sensors Replacement

A knock sensor costs AED 90 to AED 150. Besides, the mechanic charges a fee. All-in-all, knock sensor replacement can cost AED 300 to AED 500, depending on the complexity of the engine and the causes behind the failure. If the sensor has wiring issues only, it will cost less than the replacement.

FAQs

What happens when a knock sensor goes bad?

When the knock sensors go bad, the vehicle poses several issues, such as reduced power and acceleration. This happens due to incorrect valve timing and combustion. Moreover, malfunctioning knock sensors can cause car cylinder failure if not replaced instantly.

How does a knock sensor affect timing?

When an engine combusts the air-fuel mixture prematurely, the car knock sensor detects it while the ECU adjusts the ignition timing to prevent damage.

How many knock sensors does a car have?

Most car engines have one knock sensor. However, bigger engines with V6 or V8 layouts have two car knock sensors.

Is the knock sensor hard to replace?

While it is recommended to visit a professional to get the knock sensors replaced, it also depends upon the expertise of a car owner. 

This was all about the car knock sensors, a type of car sensors, that improve the engine performance. If you buy a used car in the UAE, check all the components beforehand. You can opt for the dubizzle inspection services for a detailed report on the used car.

Stay tuned to the dubizzle Cars blog to learn more about various car components, their working and benefits.