5 Symptoms of a Bad Knock Sensor in Your Car

Last Updated on November 24, 2019 by themechanic

Air and fuel are supposed to be ignited by the spark plug after they’re mixed in the internal combustion chamber. However, there are some occasions when fuel explodes inside the cylinder during the combustion process. This alters the timing of the ignition, resulting in something called engine knocking. The knocking creates vibrations which are detected by the knock sensor. Once the vibrations are detected, the powertrain control module receives a voltage signal from the knock sensor. The module analyzes this information and uses it to modify the timing of the ignition accordingly. As a result, the engine does not get damaged from bad timing.

5 Bad Symptoms

The knock sensor must remain strong if you want your ignition timing to stay consistent. If the knock sensor were to ever go bad, then it would create a lot of problems for the internal combustion process. This would result in numerous symptoms which would not be good for your vehicle or for you as the driver of it. You must recognize these symptoms for what they are and bring your vehicle to the mechanic once you notice them. They will be able to replace your knock sensor in order to prevent any more of these symptoms from occurring again.

Below are the top 5 symptoms of a bad knock sensor in your car.

1) Thumping Noises

The engine will make thumping noises when the knock sensor goes bad. At first, the noises won’t be so loud, but they will be apparent. But as time goes on and the knock sensor gets worse, the thumping noises will only get louder. If you don’t fix this problem fast enough, it could damage the engine. So, take these noises as a sign that you need to replace your knock sensor at once.

2) Check Engine Warning Light

Any weird or unusual things that occur in the engine will result in the Check Engine warning light coming on. A bad knock sensor is one of these things because the powertrain control module cannot receive an accurate reading of the engine knocking vibrations. Since this throws off the ignition timing, it interferes with the internal combustion process. Therefore, the warning light comes on.

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3) Weak Acceleration

If you step on your gas pedal to accelerate but the vehicle does not go much faster, then it is possible that your knock sensor has gone bad. Of course, it will be impossible to make this diagnosis on just weak acceleration alone. If you’re experiencing the other symptoms on this list, then it is more likely because of a bad knock sensor. Only a mechanic will know for sure.

4) Weak Engine Performance

There are many reasons why your engine performance may be lacking. If you’re already experiencing weak acceleration and thumping noises, then it is likely due to a bad knock sensor. Your engine will reveal more symptoms too. For instance, the vehicle will start to jerk around a lot and feel like it’s dragging on the road. In some instances, you’ll experience a burning smell in the cabin too. If this goes on any further, it may cause irreversible damage to the engine.

5) Poor Fuel Economy

A bad knock sensor will reduce the fuel economy of your vehicle. You’ll get a couple of miles per gallon less than usual, which means more trips to the gas station to refill your gas tank. You may not immediately think your knock sensor is the cause of this problem. But it is likely the case if you’ve experienced at least 2 or more of the symptoms mentioned on this list.

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