Is your Subaru’s Engine Knocking? Here’s How to Tell and What to Do About It

Subaru cars are known for their durability and reliability, but engine knock can be a common issue for some models. Engine knock, also known as detonation, is a knocking sound that can occur in the engine when the fuel-air mixture detonates prematurely in one or more cylinders. It can lead to serious engine damage if not addressed promptly. In this article, we’ll explain what engine knock sounds like in a Subaru, why it happens, and how to identify and address it.

What does engine knock sound like in a Subaru?

Engine knock can sound like a metallic knocking, pinging, or rattling sound that increases as you accelerate. It usually occurs when the engine is under load or when you’re driving uphill. Some Subaru owners have described it as a "tinking" or "pinging" sound.

Why does engine knock happen in Subarus?

There are many factors that can contribute to engine knock, including low-quality fuel, overheating, engine deposits, and incorrect ignition timing. In Subarus, engine knock can also be caused by faulty knock sensors, which are designed to detect and prevent knock. Some Subaru models, such as the WRX and STI, are more prone to engine knock due to their high-performance engines and turbochargers.

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Identifying engine knock

If you hear a knocking sound coming from your engine, it’s important to identify whether it’s engine knock or another issue. Here are some tips for identifying engine knock:

  • Listen for a metallic knocking or pinging sound that increases as you accelerate.
  • Check if the sound goes away when the engine is idling or under light load.
  • Pay attention to the sound when the engine is cold and warmed up.
  • Monitor your car’s performance, such as reduced power or fuel efficiency.

Types of engine knock

There are two main types of engine knock: spark knock and compression knock. Spark knock is caused by the fuel-air mixture detonating too early due to high cylinder pressure or hot spots in the combustion chamber. Compression knock occurs when the air-fuel mixture is compressed too much and detonates before the spark occurs. Both types of knock can cause serious damage to the engine if left untreated.

Addressing engine knock

If you suspect that your Subaru engine is knocking, there are several steps you can take to address the issue:

  1. Use high-quality fuel with the correct octane rating. Avoid using low-quality or ethanol-blended fuel, which can cause engine deposits and knock.
  2. Check and replace the knock sensor if necessary. Faulty knock sensors can cause false signals that lead to engine knock.
  3. Inspect and clean the engine components, such as the spark plugs and fuel injectors, to remove deposits and improve engine performance.
  4. Adjust the ignition timing or replace the timing belt if necessary. Incorrect timing can cause engine knock.
  5. Seek professional help if you’re not confident in addressing the issue yourself. A mechanic can diagnose the problem and recommend the best course of action.
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Frequently Asked Questions

Q: Can engine knock damage my Subaru’s engine?

A: Yes, engine knock can cause serious engine damage if left untreated. It can lead to worn or damaged engine components, such as pistons and bearings, which can be expensive to repair or replace.

Q: Can I continue driving if my Subaru’s engine is knocking?

A: It’s not recommended to drive your car if the engine is knocking. Continued driving can cause further engine damage and increase the risk of engine failure.

Q: How can I prevent engine knock in my Subaru?

A: You can prevent engine knock by using high-quality fuel with the correct octane rating, avoiding aggressive driving, regularly maintaining your car, and addressing any issues promptly.


Engine knock can be a common issue for Subaru owners, but it’s important to address it promptly to prevent serious engine damage. By knowing what engine knock sounds like in a Subaru, why it happens, and how to identify and address it, you can keep your car running smoothly for years to come. Remember to always use high-quality fuel, regularly maintain your car, and seek professional help if you’re not confident in addressing the issue yourself.

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Billy Covington

With a passion for all things automotive, Billy is our go-to expert on Subaru performance upgrades and modifications. He's been featured in several car magazines and blogs, and his extensive knowledge and expertise make him a valuable member of our team. When he's not working on cars, he enjoys playing guitar and writing music.

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