Can Bad Knock Sensors Cause Rough Idle?

Determining the causes of our car troubles can sometimes be an arduous task. With so many things contributing to one function simultaneously, it can be a little frustrating. Knowing some of the basics is essential to increase your safety and vehicle maintenance record.

In this article, we will be looking critically at the relation between your car’s rough idling and faults from the knock sensor. We will also be answering some related questions to help you understand some essential workings of the two.

Can a Bad Knock Sensor Cause Rough Idling?

Yes, a bad knock sensor can cause your vehicle to rough-idle, albeit more indirectly. While this may not be your first thought when the situation arises, it is a strong possibility. It is not among the more common causes: a vacuum leak, faulty spark plugs, carburetor issues, or dirty fuel injectors. However, there exists a connection and interaction between the two.Can Bad Knock Sensors Cause Rough Idle

What is a Knock Sensor And a Rough Idle?

A knock sensor is a small cylindrical component attached to your car’s engine. It is usually black and rubberlike and can be seen below the vehicle in many car models. The knock sensor is tasked with the primary function of detecting abnormalities in your engine and sending feedback to your automobile’s computer. It detects pings and knockings in your engine caused by pre-ignition, abnormal combustion, or untimely detonation. It is essentially a listening device attached to your engine to alert you of any mishaps that may not be audible to you.What is a Knock Sensor And a Rough Idle

Rough idling is simply experiencing mild or high signs of turbulence/vibration while your car is not moving. In mild cases, you will feel these vibrations mostly from your steering wheel and, if it progressively gets worse, from the entire vehicle.

Also Know: Why Does My Steering Wheel Shaking And Making Noise?

What Happens When a Knock Sensor Goes Bad?

Some common causes of engine shaking are problems within some of its components being unable to perform their function or functioning improperly. The knock sensor’s job is to detect most of these abnormalities in time and report so. Suppose your spark plugs are becoming worn out and unable to ignite correctly. In that case, it transfers this feedback in time to avoid any further mishap to your engine.What Happens When a Knock Sensor Goes Bad

There are no immediate effects or issues that may arise if your knock sensor goes bad. Nevertheless, leaving it like this can seriously affect your car’s health and your pocket in the long run. Many things happen while a vehicle is or is about to run, and mishaps may occur, and while some are audible to the human ear, many are not. Thus, driving without a knock sensor is okay but not recommended.

Knock sensors, in most cases, do not go bad at once. Instead, its efficiency gradually depreciates. It gets to a point where it either completely fails or sends wrong signals to your car ECU or PCM before dying completely.

If it sends alerts to your car wrongly, it may make you think your vehicle is knocking when it is not. It also causes the ECU to try adjusting ignition timing to correct the problem, which wasn’t there in the first place. Thus, resulting in engine hesitation (sluggishness) or jerking/vibration.

Some telltale signs of a bad knock sensor are poor car acceleration, high fuel consumption, and a sluggish engine. Also, check for engine shaking that results in a code warning or shaking that results in a service engine light. Thumping noises that get progressively louder is also a sign.

Can a Bad Knock Sensor Cause a Misfire?

Yes, a faulty or lousy knock sensor can cause your engine to misfire as it starts, and unusual vibrations usually follow this misfiring throughout your car.

How Do You Troubleshoot a Knock Sensor?

There are several reasons why your knock sensor develops faults. These reasons range from simple corrosion and incorrect mounting to short circuits, wiring breaks, and mechanical damage.How Do You Troubleshoot a Knock Sensor

Troubleshooting your car’s knock sensor may be a bit technical if you are not savvy. We advise you to visit your mechanic for an adequate diagnosis. Nonetheless, there are a few things you can do.

Firstly, check that the sensor is correctly fitted and tightened. Next, check for electrical breaks, askew wires, incorrect connection, and corrosion. If it shows a code warning, read the code and compare it with the manufacturer’s stored fault code in the factory code list. For older cars, checking the ignition point will be helpful.

There are more mechanical processes like sounding out with a multimeter which your mechanic may do if he suspects a fault but not detected from the above.

Can You Drive With a Bad Knock Sensor?

Yes, you can fully drive without a knock sensor though some new-age automobiles may slow down the timing to help you not do further damage to your vehicle.

However, driving without it is not advantageous to you or your car because;

  • You will burn way more fuel than is typical.
  • A faulty knock sensor can send wrong signals that may cause stalling, sluggishness, and other issues.
  • A bad knock sensor can cause you to be ignorant of problems with your engine that may lead to its total failure.

Also Know: Is Driving With a Bad Camshaft Sensor Safe?


Conclusively, knock sensors can cause rough idling, stalling, and misfires when they are not functioning correctly. When you notice the symptoms of a bad knock sensor, it is vital to troubleshoot and repair it. You can drive with a bad knock sensor with minimal issues. However, it is an essential part of your car working, and we recommend fixing it as soon as possible to keep your engine in good health.