Six Causes of Engine Knock and How to Fix it

There are many different sounds that car engines make, some more intense than others.

Engine knock can cause damage to many components of your engine and is something you don't want.

Engine knock is usually quite simple to fix. We will discuss the main causes and the ways to fix them in this article. Let’s begin with a quick overview of the common causes:

A knocking engine can be caused by either a poor knock sensor or the incorrect fuel type. An incorrect ignition timing or lean fuel mix can cause an engine to explode.

These are some of the most frequent reasons that an engine knocks. This is a more comprehensive list of most likely causes for a car's engine to knock.

Causes of knocking on a car engine

1. Low Octane Rating

Most likely, your engine knocks during acceleration because you are using the wrong fuel or fuel with low octane ratings.

You either refilled incorrectly the previous time at the station or the station had an issue with their fuel.

Premature combustion can occur if you use fuel that has a low octane rating. The engine will knock as a result.

The problem could have occurred when you had to refill fuel. If you're not sure, an octane booster might be able to help you boost the octane.

2. Bad Knock Sensor

Bad knock sensors are the next most common reason for engine knock. The knock sensor is made for exactly this purpose – to prevent engine knocks.

Engine control is always looking for a more advanced ignition to achieve higher performance. To avoid engine knock, you should fill up your tank with low-octane fuel.

Therefore, the engine knock sensors’ job is to monitor for any knocks and, if one occurs, tell the engine to retard the ignition further to prevent engine damages. A bad engine knock sensor can cause engine knock by sending false signals to engine control units.

3. The wrong ignition timing

An engine that is too sensitive to ignition timing could cause it to begin pinging and/or knocking. An engine can knock if the ignition timing is not correct.

However, it does not apply to an older vehicle with either an adjustable distributor timing or a crankshaft or cam position sensor.

The ignition timing is controlled entirely electronically in newer vehicles, meaning that it will be impossible to alter the timing.

An ignition timing light is required to inspect the timing of an older car that has adjustable ignition timing. You can slow down your timing to test whether it affects the engine's detonation. For the best ignition timing, it is recommended that you refer to the manual.

4. Lean air/fuel mixture

You maybe didn’t know it, but the fuel entering the engine is also cooling the combustion chamber. The fuel/air mixture will cool less efficiently if it is not too rich. This will result in a lot more heat inside the combustion chamber.

The heat could cause the mixture of air and fuel to ignite itself before the spark plug can send its spark. This will result in the engine starting to knock. These types of destinations are hazardous for your engine’s internal parts and can melt down your pistons quickly.

5. Wrong spark plugs

Although it is rare for spark plugs to cause engine knock and detonation, this could happen.

The spark plug is what ignites the mixture of fuel and air. You can get engine knocking from incorrectly chosen spark plugs.

The spark may be too weak in the first case, but it might not spark properly in the second. To ensure the correct model of spark plugs is used, check your vehicle's manual.

6. Additional Engine Knocking Sound

There is also a chance that it isn’t engine knock or pinging you hear from your engine; it can be some type of other engine noise.

It is possible that it sounds only while you are accelerating. However, if it makes a constant noise it could be engine knocking or pinging.

Other common things that could make knocking noises include the timing or serpenting belt tensioners/pulleys and bad rod bearings.

Find out more: Common Car Engine Sounds

Engine Knock is what?

High heat can cause engine knocking, or pinging. This happens when an air-fuel mixture becomes self-ignited prior to the spark plug being ignited. This can happen due to a bad ignition timing, low fuel octane or lean mixture of air-fuel and diesel.

The engine will start to heat up halfway. This will create incredible pressure as the piston still has half the distance before reaching the top. It can also cause extreme heat which could melt your pistons or cylinder heads.

You should fix it as soon possible.

How to Repair Engine Knock

You now know what causes engine knock and how to fix it.

You must first remember when the knocking started. It is possible that the fuel tank has a problem. This can be fixed by either replacing the fuel or using an octane boost.

A diagnostic scanner can be used to check for trouble codes that may relate to knock sensor/s. It is time to replace or repair the knock sensor if you discover any problem codes.

Also, make sure to inspect the spark plugs for the right type of spark plug for your car. To find the correct spark plugs, consult your manual.

It is important to adjust the ignition timing for older cars and modified models. To find out whether your timing is adjustable, consult the repair manual.

If you don't know how to adjust timing, a professional repair shop will do the job. They also have special tools that you need for this procedure.

Engine Knock FAQ