9 Insightful Symptoms of A Bad Knock Sensor [+ Video]
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A bad knock sensor will limit an engine's performance, as the engine will not be able to adjust the timing of the spark plugs correctly. The engine may run rough and experience a lack of power, stalling, hesitation, and poor fuel economy.
There may also be an illuminated check engine light, and a diagnostic scanner may reveal an error code related to a bad knock sensor.
A faulty knock sensor can also cause a misfire, resulting in a decrease in engine performance and an increase in exhaust emissions.
The oxygen sensors may also be affected by a damaged knock sensor, as the oxygen sensors will not be able to measure the oxygen content accurately. This can result in an incorrect air-fuel ratio and further reduced engine performance.
In this article, we will discuss the various symptoms of a bad knock sensor.
Table of Contents
Understanding Knock Sensors Video
What is a Knock Sensor?
A bad knock sensor is an electronic device mounted in the engine that senses vibration and detonation.
The knock sensor sends data to the vehicle's computer, which adjusts the ignition timing accordingly to prevent engine damage from pre-ignition or detonation.
When the knock sensor fails, the computer does not receive the correct information, and the engine will not be able to adjust the timing correctly.
What are the Functions of a Knock Sensor?
The function of a knock sensor is to detect engine vibration or detonation and send signals to the vehicle's computer.
The computer then uses this information to adjust the ignition timing so that the engine runs smoothly without pre-ignition or detonation.
A knock sensor can cause the engine to run roughly and with a lack of power, as the timing cannot be adjusted correctly. The functions of a knock sensor include the following:
1. Ignition Timing Adjustment
The knock sensor detect engine knocking, pinging, or abnormal combustion. The sensor then sends a signal to the engine's computer, which adjusts the timing of the spark plugs to prevent knocking.
2. Detonation Detection
The knock sensor is also used to detect engine detonation caused by the build-up of too much pressure in the combustion chamber.
When detonation occurs, the knock sensor will signal the computer to reduce engine power and protect the engine from damage.
3. Performance Tuning
The knock sensor is used to help tune an engine for maximum performance. By monitoring the engine’s knock levels, the computer can adjust the ignition timing and fuel delivery to optimize power and efficiency.
4. Diagnostics
In addition to detecting engine knocking and detonation, the knock sensor can also detect other engine problems, such as a vacuum leak.
By monitoring the knock signals, the computer can identify potential problems and alert the driver to take corrective action.
Symptoms of Bad Knock Sensor
The symptoms of a bad knock sensor are a rough running engine, lack of power, stalling, hesitation, poor fuel economy, illuminated check engine light, and diagnostic scanner error codes related to the knock sensor.
It can also cause a misfire and incorrect air-fuel ratio, further reducing engine performance and increasing exhaust emissions.
1. Rough Running Engine
A rough running engine is a symptom of a bad knock sensor. When the sensor fails, the computer does not receive the correct information, and the engine cannot adjust the timing correctly.
This can result in an uneven running of the engine, as the engine will misfire due to incorrect timing. The engine may hesitate when accelerating, stall, have reduced power, and run rough.
2. Lack of Power
Lack of power is a symptom of a bad knock sensor. When the sensor fails, the computer does not receive the correct information, and the engine cannot adjust the timing correctly.
This can decrease engine performance, as the engine cannot generate enough power to run efficiently.
3. Stalling
Another symptom of a bad knock sensor is stalling. When this happens, the computer will not be able to properly adjust the timing, which can cause the engine to stall. This issue can occur when the vehicle lacks air or fuel.
4. Hesitation
The hesitation of the car engine is also a symptom of a bad knock sensor. When the sensor fails, the computer does not receive the correct information, and the engine cannot adjust the timing correctly.
This can result in the engine hesitating when it is being accelerated, as the engine is not running at the correct speed.
5. Poor Fuel Economy
A bad knock sensor can cause poor fuel economy. The computer will need to be able to determine the correct timing, which could result in the engine using more gas than it should. The vehicle will also start to sputter and stall.
6. Illuminated Check Engine Light
The illuminated check engine light is a symptom of a bad knock sensor. When the sensor fails, the computer does not receive the correct information, and the engine cannot adjust the timing correctly.
This can result in an illuminated check engine light, as the computer is detecting an error in the engine.
7. Diagnostic Scanner Error Codes Related to the Knock Sensor
Diagnostic scanner error codes related to the knock sensor are another symptom of a bad knock sensor.
When the sensor fails, the computer does not receive the correct information, and the engine cannot adjust the timing correctly.
This can result in error codes being thrown by a diagnostic scanner, as the computer detects an error in the engine.
8. Misfire
Misfire is a symptom of a bad knock sensor. When the sensor fails, the computer does not receive the correct information, and the engine cannot adjust the timing correctly.
This can result in the engine misfiring, as the engine is not running at the correct speed.
The misfire can cause a decrease in engine performance and an increase in exhaust emissions.
9. Incorrect Air-Fuel Ration
An incorrect air-fuel ratio is a symptom of a bad knock sensor. When the sensor fails, the computer does not receive the correct information, and the engine cannot adjust the timing correctly.
This can result in the incorrect air and fuel ratio, as the engine needs to run at the correct speed. This can further reduce engine performance and increase exhaust emissions.
The incorrect air-fuel ratio can be detected by using an oxygen sensor. The oxygen sensor measures the oxygen content in the exhaust and sends the data to the vehicle's computer.
The computer then tries to adjust the air-fuel ratio with the data, so the engine runs efficiently. If the oxygen sensor detects an incorrect air-fuel ratio, it can indicate a bad knock sensor.
What are the Causes of a Bad Knock Sensor?
The causes of a bad knock sensor can be due to a damaged or faulty sensor, a clogged air filter, or a faulty spark plug.
A bad knock sensor can also be caused by engine damage, such as a cracked engine block, cylinder head, or excessive heat or vibration.
- Damaged or faulty sensor: The sensor can become damaged or faulty due to age, wear and tear, or extreme temperatures.
- Clogged air filter: A clogged air filter can cause the knock sensor to malfunction, as the sensor will not be able to detect the engine vibrations correctly.
- Faulty spark plug: A faulty spark plug can cause the knock sensor to malfunction, as the sensor will not be able to detect the engine vibrations correctly.
- Engine damage: Engine damage, such as a cracked engine block or cylinder head, can cause the knock sensor to malfunction, as the sensor will not be able to detect the engine vibrations correctly.
- Excessive heat or vibration: Excessive heat or vibration can cause the knock sensor to malfunction, as the sensor will not be able to detect the engine vibrations correctly.
How to Fix a Bad Knock Sensor?
The best way to fix a bad knock sensor is to replace it with a new one. The old sensor should be replaced with a new knock sensor that is compatible with the vehicle.
The vehicle should then be taken to a mechanic for a diagnostic scan to ensure the new sensor is properly calibrated and functioning.
- Disconnect the negative battery cable: The negative cable should be disconnected to prevent any electrical shorts or damage to the vehicle's electrical system.
- Remove the old sensor: The old knock sensor should be removed from the vehicle, taking care not to damage any of the wiring or other components.
- Install the new sensor: The new knock sensor should be installed in the same position as the old sensor, making sure to reconnect all the wiring.
- Reconnect the negative battery cable: The battery cable should be reconnected to the battery.
- Have the vehicle scanned: The vehicle should be taken to a mechanic for a diagnostic scan to ensure that the new sensor is properly calibrated and functioning.
How Much Does a Bad Knock Sensor Cost?
The cost of a bad knock sensor often varies depending on the make and model of the vehicle.
Generally, the cost of a new knock sensor ranges from $50 to $150, depending on the vehicle. Labor costs can also vary but typically range from $50 to $100.
How Long Does a Knock Sensor Last?
A knock sensor typically lasts between 50,000 to 100,000 miles, depending on the make and model of the vehicle.
If the engine is running hot or experiencing excessive vibration, the knock sensor may need to be replaced sooner.
