Engine knocking is probably the scariest sound you may hear from your car while driving. If the car shuts off after the engine knocks, it indicates a long list of problems.
If the engine is knocking and the car shuts off, low-quality fuel or bad engine timing can be the main reasons. Besides, a lean air-fuel mixture or a faulty knock sensor can cause this problem. Carbon buildup or worn rod bearings can also be responsible for the knocking.
To solve the problem, you need to
- Use high-octane fuel
- Tune the ignition timing
- Clean fuel filters
- Replace the knock sensor
- Clean carbon deposits
- And replace rod bearings
I will elaborate on the reasons for this problem with step-by-step solutions. Follow the guide till the end.
Table of Contents
Engine Knocking Car Shuts Off: How to Solve This Problem?
Let me tell you why the problem happens and how you can deal with it.
1. Using Low-Quality Fuel
The quality of gasoline is determined by its octane number. If the octane number is high, the fuel produces less knocking in the engine. The user manual of your car should have the recommended octane number for the fuel. If you use a fuel that has a lower octane number, it will cause engine knocking. Fuels with an octane number of 91-94 are considered premium.
What to Do?
1. Check the user manual for the right grade of fuel for the car.
2. Always use fuel that conforms to the manufacturer’s recommendation. It will improve the engine performance and fuel efficiency.
2. Bad Engine Timing or Pre-Detonation
In modern cars, computers determine when to fire the spark plug and ignite the air-fuel mixture. The timing is crucial to ensuring the optimum combustion inside the engine. If the ignition timing is off due to spark plug issues or gasoline issues, the spark plug may ignite the air-fuel mixture before it needs to.
This is known as pre-detonation, which causes a loud knocking noise from the engine. The firing sequence of spark plugs should also be correct according to the engine specifications. If the sequence is tangled, multiple cylinders can fire at the same time. At one point, the engine will stall for this reason.
What to Do?
1. I have already told you the first step, which is to use high-quality fuel.
2. The next step is to adjust the engine timing. You should hire an expert mechanic to adjust the ignition timing of the spark plugs because it is a very sensitive task. Don’t try to fix it yourself unless you have extensive experience in this. It may cost about $100-200.
3. Lean Air-Fuel Mixture
The engine needs an air-fuel mixture in the right ratio to be efficient. If there is too low fuel in the mixture, it is called a lean mixture. It is caused by clogged fuel filters, faulty mass airflow sensors, or faulty fuel pumps.
If the mass airflow sensor is bad, it can’t control the airflow. So, the air-fuel mixture can be lean. In that case, the car throws code 84, and engine power is reduced.
What to Do?
1. You should clean the fuel filter first. Then, clean the fuel injectors so that they can spray the fuel properly. I suggest using the ALLOSUN Fuel Injector Cleaning Kit to test the injectors properly. It costs about $34.
2. Also, check if the mass airflow sensor and fuel pumps are working correctly. If not, you need to replace those components.
3. If the problem persists, you must contact a mechanic to adjust the air-fuel ratio.
4. The Knock Sensor Is Faulty
The latest cars come with engine knock sensors that can detect the lowest possible knocks. These sensors signal the ECM or engine control module about the knocking, and the ECM takes necessary actions to reduce the knocking.
But if the sensor is faulty, the ECM can’t detect the problem. So, the knocking will increase gradually, and the car will shut off. The knock sensor code keeps coming back even if you reset the code without fixing the issue.
What to Do?
1. Use a diagnostic scanner to read the error code on the vehicle.
2. Match the code with the list of codes given in the user manual. If the code is P0325, the problem is with the knock sensor. You should get it replaced.
3. Take the vehicle to a repair shop to replace the faulty knock sensor. It will cost about $100-150, including parts and labor.
5. Carbon Buildup in the Combustion Chamber or on Spark Plugs
Regular combustion causes carbon deposits inside the combustion chamber and on the spark plugs. If you don’t clean this buildup regularly, it will cause knocking. When the deposit is too much, the engine may shut off due to the knocking.
What to Do?
1. You will find fuel system cleaners out there. Use these cleaners regularly to dissolve the carbon buildup and remove them. Also, clean the carbon deposit on the spark plugs. Fuel system cleaners may cost about $10-20.
2. I suggest taking the car to a repair shop every 20,000-30,000 miles for a full-scale carbon cleaning service. This will result in a much better performance from the engine. It may cost about $200-300.
6. Worn Rod Bearings
Piston connecting rods move the pistons back and forth to keep the engine running. To move smoothly, they need bearings. Over time, these bearings wear out. So, the normal movement of piston rods is restricted.
For this reason, there can be a knocking sound from the engine. If the bearing condition is too bad, the engine may shut off. This is a risky situation, and you may need to spend a lot on repairs or rebuilds.
What to Do?
1. Take the vehicle to a good repair shop. The engine should be disassembled to expose the rods and bearings.
2. Mechanics will check the bearing conditions and ensure the components are properly lubed.
3. If the bearings are too worn or damaged, you need to replace the rod bearings. It might cost about $1,500-$2,500, including parts and labor.
People Also Ask
You should know the answers to some commonly asked questions about engine knocking and car shutting off.
Does engine knocking damage the engine?
Yes. Engine knocking does irreversible damage to the engine. If there is too much knocking, the pistons, inner cylinder walls, and other components can be damaged badly. You may need some expensive repairs or a complete engine rebuild.
Can a rich air-fuel mixture cause knocking?
If the air-fuel mixture is rich, it will have a higher amount of oil than required. As a result, there will be air pockets in the mixture. It may cause low knocking sounds or tapping sounds from the engine.
Can I drive a car if the engine shuts off due to knocking?
Car shutting off due to engine knocking is a serious problem. The engine might have problems starting again. Even if it starts, you shouldn’t drive the car. Diagnose the reasons and fix the problem immediately.
Conclusion
I want to alert you once again about the engine knocking. The problem can become so intense that the engine will shut off. If the engine knocking shuts the car off, you may be in deep water.
To avoid severe consequences, you should check the fuel quality, fuel filter, and ignition timing. Besides, you should check and replace faulty components like a bad knock sensor or worn rod bearings.
You should also clean the carbon deposits from the combustion chamber and the spark plugs. Taking these steps will stop the engine knocking and prevent further damage.
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