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Can a Bad Knock Sensor Damage the Engine?


If you’re reading this, you might be wondering can a bad knock sensor damage the engine?

Yes, a bad knock sensor can be the cause of engine damage. A faulty knock sensor can result in increased fuel consumption, but that’s not it. If you fail to replace a bad knock sensor in time, you could end up with a damaged engine.

Therefore, it’s important that you replace your vehicle’s knock sensor before it forces you to replace your engine. After all, that’s a much more affordable option.

In this post, we’ll tell you:

  • How do knock sensors work
  • Why should you keep it functioning
  • Can you run a car with a bad knock sensor?
  • And, more

So, if you want to know everything about knock sensors, continue reading.

What is Engine Knocking?

Engine knock is caused by unwanted or second combustion in an engine’s cylinders. The rapid combustion causes the air/fuel mixture to ignite prematurely, resulting in a sharp knocking sound from the engine. This can be caused by a variety of factors, including:

  • A lean fuel mixture (too much air and not enough fuel)
  • Inadequate compression ratio
  • A worn-out or incorrectly adjusted ignition timing
  • And, more importantly, the failure of the knock sensor

What is Knock Sensor?

Generally, the purpose of sensors is to detect any activity or physical movement. A car knock sensor is no different.

A knock sensor is a device that detects knocking in a car’s engine. This device is typically installed on top of the engine block and keeps it working properly.  

It tells you whenever your car’s engine starts knocking and is an important part of your vehicle since knocking can be dangerous to the health of your engine.

The function of a knock Sensor

Early detonation and preignition can be pretty damaging to your car’s engine. And, without a knock sensor, there’s no way of knowing whether your engine is doing that or not. So, in order to stay informed about your engine’s health, you need a functioning knock sensor.

The good thing is that a knock sensor isn’t expensive, whereas, you’d have to pay through the nose should anything happens to your engine.

Symptoms of a Bad Knock Sensor

Engine knock refers to the phenomenon when the combustion in your engine occurs earlier than it should. This early detonation is typically referred to as an engine knock. An engine knock practically means that your engine creates a knocking sound when such a detonation occurs.

Engine Warning Light

One of the first things you might notice after your vehicle’s knock sensor goes bad is the warning light on the engine. But, keep in mind that there can be other reasons for your engine warning light turning on. One of those reasons is a bad knock sensor.

Loud Sounds

Another symptom of a bad knock sensor is loud thumping sounds emanating from underneath your car’s hood. The more you use your engine without fixing the problem the louder the sound gets.

Poor Fuel Mileage

If you notice a decrease in your car’s mileage per gallon, it could mean that the knock sensor isn’t doing its job properly. Again, there can be other reasons for a decreased fuel milage, one of them is a malfunctioned knock sensor.

For instance, not enough gas in tires can lead to lower fuel mileage. Similarly, a bad spark plug can also impact how long your ride runs per gallon.

Bad Acceleration

If you feel that pressing your car’s gas pedal isn’t moving it as fast as it used to, it could be a sign that your knock sensor has stopped working.

But, again, that alone doesn’t imply that you have a bad knock sensor. You need more proof, so what you can do is also take into account the previous symptoms. If all of that stuff is happening, it’s likely that the problem lies with the knock sensor.

Reduced Engine Performance

One of the worst symptoms of a bad knock sensor is damaged or broken engine components. And if you feel your car’s engine isn’t performing as it used to, you need to take it to your mechanic.

But, how exactly can you know that your engine performance has deteriorated? Observe performance issues like:

  • A burning odor from the engine
  • Car jerking while accelerating

Knock Sensor Replacement Cost

If you don’t fix a bad knock sensor in time, you’d end up compromising the life of your engine. But, how much does a knock sensor cost? If you have a standard vehicle, expect to invest anywhere from $120 to $500 for a knock sensor replacement, including the parts and labor cost.

mechanic installs a knock sensor on car engine

Can You Drive With a Bad Knock Sensor?

Yes, you can drive with a bad knock sensor, but the real question is, are you willing to pay the price? See, the knock sensor is responsible for keeping your engine safe and healthy. Just keep in mind that an engine replacement can be around $4000 to $5000, and a bad knock sensor can lead to a failed engine.

Bad Knock Sensor Causes

There can be several reasons for a knock sensor going bad. Here are a few prominent ones:

  • An overly rich fuel-air mixture
  • Worn out valves and piston rings
  • Misfiring spark plugs

Final Thoughts

Can a bad knock sensor damage the engine? Yes, a bad knock sensor not only damages the engine but can also reduce its life. By now, you should know the importance of replacing a bad knock sensor.

Replacing a knock sensor isn’t nearly as expensive as replacing an engine. The good thing is that you know the symptoms of a bad knock sensor. So, if you’re experiencing any of these, it’d be a good idea to get the knock sensor checked and have it replaced.

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