Engine Started Knocking Then Died [Reasons + Solutions]

The main reasons behind the engine started knocking then died are low fuel quality, low oil level, lean fuel mixture, bad engine deposits, no dielectric grease, loose timing belt, and bad rod bearings.

Keep reading this article to find out more about what causes engine knocking in detail and learn how you can fix them. Let’s begin!

Engine Started Knocking Then Died [Reasons + Solutions]

It’s difficult to know if the sound of knocking from the engine is caused by simple issues or major engine problems. There’s no way to tell unless you listen to the sound and start to diagnose the problem.

But it’s important to act quickly as the knocking noise in the engine can lead to bigger problems if it’s not resolved at the appropriate time. Here are all the common reasons that cause the knocking sound of a car engine. Some of them are easy to fix and some of them are hard.

Note: You can also read how to fix Engine ran without oil now knocking problem.

1. Low Fuel Quality

You can hear an engine tapping noise if you put fuel of low quality in your car. Most engines that are high pressure require higher-octane fuel to function well. If you ignore that to save a few bucks, it can cause the engine knock that nobody likes.


If you have an engine knocking issue, you better hope that low fuel quality is the culprit behind this issue. That’s because it’s easy to fix. All you have to do is refer to your owner’s manual and use the octane that is recommended by your car manufacturer.

There’s a reason why they recommend the type of fuel they do. Different brands have different additives and that too can create the problem. If you get the engine knocking sound after changing from a specific gas station, take note of it and consider going to another one.

2. Low Oil Level

It’s common to hear a knocking sound on the car if you have a low level of oil and it’s almost running out of oil. You can check if the oil level is too low with a dipstick.


It’s time to refill your oil if you find that the oil level is low. Drain the old oil first and put the new oil back in. Change your oil filter when you add the new oil to ensure that your car runs well.

3. Lean Fuel Mixture

When the ratio of air and fuel isn’t right, it forms a bad mixture. A lean mixture happens when the fuel in the car isn’t enough to match the air. The engine pings and gives a knocking sound when it happens.

Other symptoms of bad fuel mixture are frequent engine misfires, rough idling of the car, the black exhaust coming from the tailpipe, and reduced performance of the engine.

There could be many reasons behind a lean fuel mixture. The most common ones are:

  • Malfunctioning oxygen sensor.
  • Bad fuel pressure regulator.
  • Damaged fuel injectors.
  • Faulty Mass Airflow Sensors.
  • Bad Engine Coolant Temperature Sensor.
  • Faulty ECU.


Identify the root cause of the problem that’s causing the lean air mixture problem. Whatever has gone bad needs to be replaced to fix this issue.

4. Bad Engine Deposits

One of the consequences of using fuel of lower quality is the build-up of harmful deposits in the engine. If your car is making a knocking noise, it could be because these deposits are blocking the cylinders.


Inspect your car and see if there is a build-up of carbon deposits in your car. Clean your vehicle thoroughly to solve the engine knocking and shaking problem. You can do it yourself by physically scraping the carbon deposits or taking your car to an automotive store.

5. No Dielectric Grease

The lack of dielectric grease in the connectors is a common issue in trucks that keeps the car from starting. The absence of it creates a bad connection and makes the engine misfire.


Add the appropriate amount of dielectric grease to get the truck out of the “safe mode” and regain power. It doesn’t conduct any electricity and you shouldn’t overapply it.

6. Loose Timing Belt

The timing belt is an important component that connects the crankshaft and camshaft of the engine and controls the valves and pistons in the vehicle. When the timing belt gets too loose, it can cause a knocking sound and keep the car from starting.

Bad timing can also be caused by faulty sensors in your car. If the ECU tells the spark plug to fire at the wrong time, there will be too many cylinders firing off at the same time and create that knocking sound.


The timing belt has to be replaced if it has gone bad. It can cost anywhere between $300 to $500 to replace the timing belt but you have to incur it if you want to get your car fixed.

If the timing felt is fine, start by making sure that the spark plugs are installed correctly. If the problem is with the ECU, you need to replace it.

7. Bad Rod Bearing

The bearings are supposed to stay in place in normal operation. But when one of the bearings is spun, it can create a knocking sound. Wear and tear over time can cause a bearing to spin.


Inspect each of the bearings one by one in all the cylinders to determine if they’re the ones that are causing the problem. Try to wiggle them around. The bearings that are okay should stay in place and not move around.

Check them for visible wear and tear as well. If you see signs of damage, you have good reason to say that the bearing has spun. The only solution, in this case, is to replace the spun bearing.


Can a bad spark plug cause engine to knock?

If you notice the engine knocking when accelerating, it could be due to a bad spark plug or if it’s connected the wrong way. It can be easily fixed by plugging them the right way or replacing them.

Is it dangerous to hear a knocking sound after turning the engine off?

It can be both normal or dangerous to hear an engine knocking after turning it off. It could be something as simple as the radiator cooling down or a complicated issue like a blown head gasket.

Can you drive a car with a knocking engine?

You can drive your car for a while if you hear a knocking sound until you find a safe spot to pull over. But if you continue to do so, it can lead to a major problem in your engine.

How to prevent your engine from knocking?

Use a higher octane fuel and make sure that you have sufficient oil in the vehicle. Routine maintenance and care of your vehicle will prevent the knocking sound.


Now you know the most common reasons behind engines started knocking and then dying and how you can fix them. You’re lucky if it’s one of the simple issues like using bad quality fuel as you can fix it easily. Otherwise, something like a bad rod bearing, it’s going to leave a hole in your pocket.

We hope this guide will help you pinpoint what’s causing the engine knocking issue for you and get it fixed. Drop a comment below if you have any more questions about engine knocking.

About John M

John contributed as a technical head at an automobile company just 2 years after his post-graduation in Automobile Engineering. He loves to lead a free life, so he left his job & started blogging. Now, he does research on every automotive problem, part & product and seeks a better solution & best products & shares his findings with his readers to help them as well as to minimize their struggle.

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