What is Engine Knock?
Engine knock is a knocking sound in your engine that occurs when fuel isn’t burned evenly and needs to be fixed as soon as possible to avoid major damage.
Written by Payton Ternus
Reviewed by Melanie Reiff
Engine knock can happen when your car’s engine isn’t burning fuel evenly. It can sound like there is a knocking coming from inside the engine, and it needs to be fixed right away to prevent damage to the cylinders or pistons.
Knock, knock—who’s there? A case of engine knock really isn’t a joking matter. This annoying noise can indicate serious problems under the hood of your car.
It’s important to keep your car in tip-top shape—that’s why
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super app Jerry
has put together this guide to understanding engine knock and what to do if you’re experiencing it. What is engine knock?
Engine knocking is quite literally what it sounds like—a true knocking sound coming from your car’s engine. It’s a repetitive pinging or tapping that becomes more intense when your car accelerates. This annoying sound happens when the fuel in your car’s engine is burning unevenly.
The engine cylinders burn fuel in small pockets when they have the right ratio of fuel and air. When each pocket burns, a small shock is created which ignites the next pocket and keeps the cycle going. If the fuel is burning unevenly and the shocks go off at the wrong time, you get engine knock and potential engine damage.
Key Takeaway Engine knocking needs to be fixed right away to prevent any serious damage—and expensive repairs—to the engine’s cylinders or pistons.
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What can cause engine knocking?
Engine knocking is a serious problem and needs immediate attention, but finding the source of the problem can be a little tricky. Six common causes could be behind engine knocking.
Faulty spark plugs
Each car needs a specific kind of spark plug to fit its particular machinery and engineering needs. The wrong
spark plugs
can change the heat of the spark and affect performance. Incorrect spark temperatures can result in engine knocking.Fuel-to-air mixture is disrupted
A faulty fuel injector will affect the ratio of fuel to air in the mixture entering the engine cylinders. The incorrect ratio causes the temperatures in combustion chambers to rise and changes the dynamic of the air and gas mixture under pressure. These conditions make it much easier for premature ignition to occur.
Gas with a lower octane rating
Your car’s engine is designed to burn fuel with a certain octane rating. Pressure affects how flammable fuel is, and lower octane fuel burns more easily. If you use fuel with a lower octane rating than what your car’s engine is designed to burn, the fuel can spontaneously ignite under too much pressure.
MORE: What do the gas octane ratings actually mean?
Hot spots
Hot spots are carbon buildups that retain heat. The extra heat retained in these locations can create the spark to prematurely ignite fuel while also taking up room in the cylinders.
Reduction in cylinder volume
Carbon buildups have more than one negative effect on a car engine. They can cause the previously mentioned hot spots, but they also steal volume in cylinders. This increases pressure on the fuel-to-air mixture and can cause premature ignition.
Valve impingement
There’s that pesky carbon again. If the valve stems have too much carbon buildup, the airflow is reduced. Serious cases can even prevent the valve from closing at all, resulting in a loss of compression needed for proper engine operation.
How to fix engine knocking
Now that you know what engine knocking is and what can cause it, here are the steps you can take to fix it:
- Upgrade your gasoline. Fuel with higher octane ratings can withstand more pressure before combusting. Try upgrading to a higher-octane fuel—particularly one with carbon-cleaning additives to avoid excess carbon buildup.
- Give your engine a tune-up. Help keep your engine in tip-top shape by installing new wires and spark plugs.
- Change the oil. Make sure you’re changing your engine’s oil regularly to prevent carbon buildup. You should also be keeping an eye on the oil level to make sure it isn’t getting too low.
If you’re still hearing the tell-tale knock after trying these solutions, you’ll need to take your car to an expert.
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