Engine knock On Startup Then Goes Away, What To Do?

Imagine it’s Monday morning, and you’ve just returned from a restful weekend in which you didn’t have to leave the house. You start your automobile to begin your morning trip to work, and you hear an engine knock on startup then goes away from your engine compartment. What options do we have?

We’ve identified the most prevalent causes and what you can do about them, so keep reading to learn more.

 Reasons Why A Car Engine Knock On Startup Then Goes Away

An automobile engine is meant to knock as it starts up and then goes away, but this isn’t always the case. This could be caused by a variety of issues, such as a water leak. Here are four reasons why your engine may knock before it stops working:

1. Worn-out Belt Tensioners And Pulleys

Engine banging could be caused by something other than the engine itself. It’s possible that it’s coming from the auxiliary belt. A belt attached to numerous pulleys throughout the engine room rotates when the engine runs. To turn smoothly and quietly, this belt must be under a precise amount of strain. Rattling, clicking, and slapping noises can be misinterpreted for engine knock if the belt is stretched out, the tensioner isn’t working properly, or one of the pulleys is bent out of shape. Fortunately, replacing the belt, adjusting the tension, or replacing a defective tensioner or auxiliary pulley can all solve a noisy accessory belt.

2. Wear On The Main Bearings

With a lot of miles on it, the primary crank bearing wears out a lot. The center main bearing wears out, and the crankshaft no longer has the appropriate tolerance, causing the thrust bearing to continuously hit it for many seconds until the crank heats up enough from operation to fill the open space and cease the impact for the time being. This problem will recur after the engine cools down and the crank contracts significantly.

This means it’s more likely to happen after a long amount of time with the engine turned off, and less probable when the engine is started after a quick pause. This is unlikely to cause any further mechanical concerns, and will simply be a source of noise until it is resolved. Keep an eye on your oil and make sure the bearing isn’t leaving metal shavings, or even lower the oil pan to make sure there’s no metal debris.

3. Bad Knock Sensor: Detonation Knock

Because the air/fuel ratio, fuel injectors, and timing are all computer-controlled, engine knock isn’t a common problem in modern cars. There’s also a knock sensor that detects engine knock and alerts the Engine Control Unit, allowing it to instantly repair the problem.

As a result, a faulty knock sensor might cause the engine to knock. Checking the knock sensor is an important component of the diagnostic process if you’re driving around in a modern car with an engine knock.

4. Slapped Piston

When the piston slaps the cylinder head in an attempt to go back and forth, it is known as the piston slapped. This difficulty is readily solved if you use a less expensive engine, even if it is made by a well-known brand.

Because of the higher-quality materials utilized, a well-known, more expensive engine will cost you more. They are, however, more difficult to operate because accessing all parts can be more difficult than working with a regular automobile engine.

5. Engine Lifters That Are Clingy

An insufficient supply of engine oil reaching the engine’s various components might result in a sticky engine lifter and worn-out engine seals. It may also start with a slap of the pistons or even a shock of the engine.

To fix this problem, you should change your vehicle’s engine oil frequently, apply an engine oil additive to protect engine parts, and get your engine checked at regular intervals.

How To Prevent Knocking Sound When Starting Car?

As previously indicated, engine knock-on startup that goes away might be caused by a variety of factors, including engine component wear and tear or piston slap.

If you observe these symptoms, make an appointment with your technician for a correct diagnosis, because if you ignore them, you’ll be setting yourself up for a greater problem. The sooner you can tackle the problem, the better.

Here are some recommendations for preventing engine knock-on startup that then goes away in your car.

1. Make An Investment In High-Quality Oil

Engine wear and tear can be reduced by using high-quality engine oil. Your automobile will immediately heat up each time you start it. It means that the engine parts expand rapidly, causing metal pieces to rub together. If the engine is not adequately lubricated, this can cause harm.

High-quality oil helps to improve engine performance by reducing heat generation and extending the life of engine components. It can also remove carbon deposits from engine valves and pistons, as well as reduce engine noise at the beginning.

2. Get Your Engines Tuned Up On A Regular Basis

Schedule a correct engine turning with an engine turning professional on a frequent basis to minimize misfire, carbon buildup, and engine knock-on startup. This is because an engine expert is more familiar with and understands engine behavior, making it easier to detect a problem.

Engine turning on a regular basis will improve your vehicle’s fuel economy as well as the general quality of its performance. This is performed by making appropriate engine component changes.

3. Avoid Rough Driving

If you want to save engine wear and tear, you should restrict the amount of time you spend driving aggressively. When stuck in traffic, this form of driving entails speeding up or revving your engine.

One of the main causes of piston slap on startup and damage to other engine components is that constant high speeds equal faster wear.

4. Check Engine Lights Should Never Be Ignored

Avoiding disregarding the car’s warning indications is a great way to keep it running smoothly. If you overlook warning signs like a check engine light or sputtering, you may be able to avoid engine damage by acting fast.

Cold start engine noise should never be ignored because it is a sign of engine trouble (no matter how minor the issue may be).

5. Engine Light Is Visible

Another way to avoid a knocking sound while starting your automobile is to pay attention to any engine light warning indications.

Ignoring these signals, whether it’s a typical check engine light or sputtering, can lead to a slew of issues or engine damage.

Frequently Asked Questions

Here are some frequently asked questions about engine knock on startup then goes away:

1. Is The Loud Knock When Starting The Car Gone?

Yes. This knocking sound will fade away once the engine has warmed up sufficiently. Even when the noise has subsided, the engine has been injured in some way.

As a result, if you hear a peculiar noise coming from your car, you should seek the advice of a professional.

2. How Much Does It Cost To Fix An Engine Knock?

Repairing an engine knock might cost anywhere from $100 to $500 depending on the severity of the problem. Prepare to pay up to $1,000 if worn-out components in your engine need to be replaced.

3. Is It Possible For Bad Gas To Cause The Engine To knock?

Bad gasoline, especially if it has a low octane level, can cause problems and damage to your car engine. Gasoline with a low octane level can cause your car’s engine to fail.


We’ve gone over some of the reasons why the engine knock on startup then goes away.

We also recommend using high-quality oil, taking your vehicle to a mechanic for a checkup on a regular basis, changing the oil filter on a regular basis, checking the engine light, and avoiding driving rough.

Hopefully, our suggestions may assist you in improving your position.

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