Skip to Content

Can a Bad Knock Sensor Cause Rough Idle?

Can a Bad Knock Sensor Cause Rough Idle?

Knock sensors help the vehicle alter engine activity according to the changes in the combustion chamber.

These sensors are worth it because they encounter all the engine issues by keeping a strong check on the engine’s performance.

Can a Bad Knock Sensor Cause Rough Idle? A bad knock sensor can cause rough idle by slowing the acceleration rate and altering engine performance. It cannot detect changes in engine performance and is unable to report the ECU about the problem. Sometimes, these sensors send no signal to the ECU and indicate that everything is going fine inside the combustion chamber. However, it can also over-report, resulting in false output when the control unit makes wrong decisions by limiting the injection of fuel in the chamber.

It is essential to maintain the knock sensors to avoid the engine problems like less power and rough idle.

Furthermore, the malfunctioning sensors need to be replaced to improve acceleration and emission of gases.

What does rough idle mean?

You can consider rough idle as a state of the engine when it cannot work smoothly. It shows no consistency in RPMs and keeps changing every minute.

It can reach a higher level or drops down below normal functioning, and the car cannot get started. It can also get to the minimum RPMs when you ignite a car.

It happens when a faulty knock sensor cannot detect the problems in the engine and knocking starts.

Why do bad knock sensors cause rough idle?

The bad knock sensors lose their ability to detect the unfavorable changes in the engine leading to severe damage.

It sends unreliable data to the control unit of the engine that takes the wrong decision accordingly. For example, the ECU ignites the spark plugs incorrectly and causes this issue.

The transfer of wrong information by these sensors indicates problems in the engine when it is performing correctly.

The ECU interprets the information and brings changes in fuel combustion by modulating the fuel injectors that affect fuel delivery on time.

Some of them send a wrong signal, while in a few cases, they send no signals to the control unit.

They affect an engine’s performance in both cases as no signal cannot help identify engine issues and can cause permanent failure.

An overactive sensor reports a wrong signal and affects the combustion as the fuel level in the chamber decreases.

Accordingly, it reports the problem when there is no knocking sound and the engine is working well.

So, it affects the rotation rate that cannot remain constant. Moreover, it decreases the acceleration rate of the vehicle. It is better to check the number of knock sensors in your car.

What are the symptoms of bad knock sensors? 

You can easily identify problems with knock sensors by carefully noticing the symptoms or checking their condition.

Bouncing effect

You can feel a shaking effect in your vehicle when these are not working correctly. It creates a bouncing effect, and the vehicle jumps up and down at a slow rate.

They can produce jerks or vibrations in the car that makes you feel uncomfortable.

Production of higher emissions 

The engine begins to produce higher emissions with a faulty device that begins to build up inside the combustion chamber.

It can produce a burning smell due to the accumulation of bad fuel gases, which are present inside. Moreover, the detonation inside the cylinders can also produce a bad smell.

Damaged catalytic converter

Catalytic converter deals with converting toxic emissions of gases to safe gases that cannot harm the environment.

Bad sensors can affect the functioning of catalytic converters by damaging the catalyst, which emits a high level of hydrocarbons.

These hydrocarbons escape from the chamber without complete combustion when the engine performs poorly, and the device cannot detect this change.

Inconsistent RPM count

The spark plugs can worn out when the knock sensors cannot detect the problems in an engine. These damaged spark plugs bring fluctuation in the RPMs.

They cannot ignite the fuel at the right time and affecting the acceleration. Misfires are common in automobiles due to these problems.

Therefore, the inconsistent RMP count indicates a problem with the spark plugs in the engine.

Check the Engine warning light

While driving a vehicle, you can see a check engine light on the dashboard, which indicates a problem in a sensor.

It can affect the engine performance badly and retain all the burned fumes inside the compartment.

Moreover, this warning light can also appear due to the failure of oxygen sensing devices.

Transmission problems

Delays in spark plug ignition can cause many problems in the transmission system.

It tries to fix the engine’s problem by using a different gear when there is nothing problematic to react upon.

The transmission keeps running, but the ignition time and power are affected by a faulty sensor.

How much does it cost to replace the bad knock sensors? 

You have to replace the faulty knock sensors if you want to improve engine power. However, an engine begins to give rough idle when you do not pay attention to them.

The replacement cost depends on the sensors’ price and labor cost. They can cost you around $65 to $85, while the labor cost is almost $120 to $380.

The overall cost varies according to the car model type and the sensors’ quality. High-quality products can cost you more but remain functional for an extended time.

Moreover, the repair shop matters a lot as some of them charge a heavy amount for the replacement procedures. Therefore, it is better to diagnose the problem as only a few parts need repair.

How long does it take to fix a bad knock sensor?

The time required to fix a bad knock sensor depends on the level of expertise. As a result, some people try to repair and replace these devices by themselves.

An unprofessional and amateur worker takes more time than an expert mechanic. It takes almost 40 to 50 minutes to remove the damaged devices and put the new ones in their place.

In contrast, a professional can do the task in only 15 to 25 minutes at maximum. However, you can also include the time taken to drive the vehicle to the mechanic and get back to your home.

Therefore, it is better to repair them by yourself to cut off the cost and save time.

What effect does a knock sensor have on engine timing?

This sensor controls the movement of the piston in the engine and regulates the timing. This timing relates to an engine’s ignition and is determined by the piston position.

It decides the time for the spark production inside the engine, and the fuel combustion starts. Next, it regulates the PCM, which controls the engine timing.

Moreover, it converts the vibrations in an engine to a signal, which is recognized by the control unit and alters the timing accordingly.

Any problem in the sensor can poorly adjust the ignition timing by sending the wrong signal to the ECU.

Can a faulty knock sensor cause poor acceleration?

It can affect a car’s acceleration rate by increasing or decreasing the torque production.

An efficient sensor can help increase the acceleration rate to a desired extent. While a bad one keeps you restricted and never allows the vehicle’s engine to accelerate beyond a limit.

It can negatively impact the fuel mileage and reduces it. So you have to fix the issue to get better acceleration by replacing a bad one with a new one.

What does a bad knock sensor sound like?

You can hear a pinging noise in the engine that sounds a little bit odd.

It can occur due to the pre-ignition of the fuel containing a mixture of air. This pre-ignition results in the production of excessive heat in the engine and produces a loud knocking sound.

It starts from mild thumping sounds that get even louder with time. Moreover, it occurs when the fuel begins to ignite inside the cylinder instead of the combustion chamber.

 What causes the knock sensor to go bad?

Many factors can cause the abnormal functioning of these sensors. These factors include low octane fuel and pre-ignition of the fuel.

The low-quality gasoline affects the time of spark in the engine or retard it. Moreover, the higher octane fuels are resistant to the knocking effect and turn on the engine light.

In addition, the accumulation of emission gases or the carbon residues on the sides of the chamber can also affect their working.

The temperature also plays a critical role in their functioning, and high temperatures can make them faulty or bad.

How long can I drive with a bad knock sensor?

You can drive a long distance with a non-functional sensing device when one of the two sensors is operating correctly. However, it is not recommended to drive when you have only one faulty sensor.

It allows you to drive, but the engine performance is at great risk. You can possibly drive a hundred miles without any problem or get stuck at any point.

However, it is better to protect yourself from engine damage that can cost you more than their replacement.

Related Articles:

Which Statements Apply to Leasing a Car?