Why Car Engine Knock on Startup then Goes Away

Why Car Engine Knock on Startup then Goes Away?

There are a variety of reasons why an engine may start humming and then stop. After a few minutes of warming up your car, the noise should go gone! As a result, it is possible to cause the engine to shake on beginning owing to worn-out components, sluggish lifter movement, worn out bearings, or carbon accumulation.

If you’re wondering why this is happening, don’t worry; we’ll go over it all in the next parts so you know exactly what’s going on. And we’ll go through how to avoid this from happening again, as well as how to solve the problem. Hold on tight!

Piston Slap

When the engine is started or accelerated, you may hear a noise called “piston slap.” Engine knock may be created by a piston that moves from side to side during engine rotation because it moves more when it is cold.

When your car has warmed up, there’s little risk of piston slap from the crankshaft. Piston slaps can occur for a variety of reasons, the most common of which being worn-out pistons or faulty spark plug timing.

Worn-out engine parts

Engine knock noises can also be caused by worn-out engine components. Sludge builds up in engines due to metal particles flowing into the oil as a result of worn-out engine rings and/or engine bearings.

If you notice an unusual or strange engine noise that doesn’t go away after a few minutes, it’s essential to take your automobile to a mechanic immediately. Our recommendation is that you have it looked out if it disappears, even if it does.

Sticky engine lifters

It is possible for a sticky engine lifter and worn-out engine seals to result from an insufficient supply of engine oil reaching the engine’s various components. It may also produce a slap of the pistons or even an engine jolt upon beginning.

You should change your vehicle’s engine oil often, use an engine oil additive to preserve engine parts, and have your engine tested at regular intervals to solve this problem..

Worn-out bearing

Bearings are spinning engine components that allow the movement of the engine elements in the engine block to be smooth and uninterrupted.

Piston slap or even knocking might occur at engine starts if these bearings wear out due to normal wear and tear.

Carbon buildup on engine

Carbon buildup in the engine can lead to engine knocking or piston slap when you switch on your vehicle if the engine oil is getting to the engine parts in the improper proportions, or the automobile is old.

How to Fix this?

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It’s usually nothing to be concerned about if you hear an engine knock on starter and it goes away after a few minutes of warming up, especially if you only hear it occasionally and don’t notice any other issues with your car, such as oil leaks or overheating.

However, it’s an indication that the engine has some problems that might worsen in the near future. To avoid this, take the steps outlined below and make use of engine oil treatment additives such as this one–

How to Prevent Engine Knock On Startup that Goes Away?

The slapping of engine pistons or the gradual deterioration of engine components are two common causes of engine noise. Check with a local auto repair shop if you hear an engine knocking sound when starting your car. If the problem isn’t correctly detected in time, it might mean catastrophic damage to your engine.

Additionally, you should follow these guidelines to keep your engine in peak condition-

Use Good Quality Engine Oil Regularly

Engine wear and tear may be reduced by using high-quality engine oil. Engine damage can occur if sufficient lubrication is not guaranteed when your automobile is first started because of the quick expansion of engine parts caused by friction between metal surfaces.

By lowering heat generation and extending the life of engine components, engine oil additives increase performance. Diesel engine oil additives are used to remove carbon deposits from engine valves, pistons, and combustion chambers to enhance fuel efficiency and reduce engine knock on startup.

So, before adding oil to the engine, make sure to verify your owner’s handbook or seek guidance from an expert on the recommended viscosity grade of engine oil.

Regularly Hire Engine Tuning Experts to Improve Your Vehicle’s Performance, Reliability, and Efficiency

By ensuring that the engine runs smoothly without any glitches or barriers like carbon buildup, misfiring, etc., proper engine tuning helps minimize engine knock on startup. For this reason, you should not delay taking your engine to a reputable tune-up shop for a diagnostic checkup by engine tuning professionals.

As part of regular engine tuning, modifications like altering the timing of spark plugs (to ensure that they fire at the proper time), setting up air/fuel ratio, calibrating engine sensors, etc., may assist improve your car’s fuel efficiency and overall performance.

To Prevent Sludge Buildup and Clogs, Filter Replacement is Essential

Sludge buildup in engines is a result of using dirty oil, and this can have a negative impact on performance. Engine oil must be changed often to ensure that it has no contaminants and that engine parts are properly lubricated, preventing engine start-up issues and other issues.

Don’t Drive Rough

Reduce driving your automobile excessively to avoid engine wear and tear. Aggressive driving includes speeding or revving the engine when you are stuck in traffic, which can lead to piston slap difficulties on restart and damage to other sections of the engine if you continue to drive at high speeds.

Never Ignore Check Engine Light

Avoiding ignoring the car’s warning indicators is an excellent method to keep it in good working order. You might easily avert engine damage by acting quickly if you ignore warning indicators like a check engine light or sputtering.

You should never disregard cold start engine noise since it is an indication of engine malfunction (no matter how minor the issue may be).


Following the advice in this article can help you avoid engine knock, which is a symptom that something is wrong with your engine.

The easiest approach to avoid an engine knock on startup is to get regular engine maintenance, which will remove carbon deposits and other debris that may have been causing your engine difficulties.

Because engine oil additives remove carbon deposits from combustion chambers, pistons, and valves, they extend the life of your engine and lessen the likelihood of problems like the knocking noise that occurs when you first start it. They also enhance fuel economy.

It’s advisable to keep the automobile in good condition if you’ve already had this happen and the vehicle is over a hundred thousand kilometers old, so that it doesn’t deteriorate any more. Unless the car is old enough to take it as normal wear and tear, it’s time to get it checked out by a specialist.

Frequently Asked Questions

a) Do engine knocks disappear?

When the engine achieves its ideal operating temperature, knocking should stop. It’s possible that even after the banging has subsided, the engine’s components have been harmed in some way.

In the worst-case scenario, the engine might be permanently damaged and rendered unusable. Because of this, it is critical to get a mechanic’s opinion as soon as possible if you notice any noises coming from your vehicle.

b) Does rod knock go away when the engine warms up?

What causes rod knock is an issue with the engine’s pistons and their rods. The middle set of rods is most commonly impacted by this. When you hear a knock when accelerating, it’s typically because the piston rod surface has worn down to the wrist pin, which is a common cause.

Most engine knocks are the result of either a connecting rod/crankshaft imbalance or a lack of proper valve timing. The most common causes of a rod knock, often known as a “big end knock,” are very long camshaft durations or inadequate valve clearances.

Due to manufacturing flaws, however, certain engines do squeak at high RPM. Because every engine and issue are unique, there is no one right solution to the question of whether rod knocks occur after warm-up.

c) Why does my engine knock sometimes?

In addition to the causes listed above, your engine may squeal from time to time for a variety of reasons. Running the engine rich or lean is one possibility.

Fuel will ignite prematurely if you’re running the engine at an excessively high octane. There will be no gasoline to keep the air/fuel combination from igniting if you run the engine too low. Knocking noises are also possible as a result of this.

d) How much does it cost to fix engine knock?

If the problem is severe or if a specific repair is required, engine knock repair costs might vary widely. However, on average, the repair of engine knock costs $500.

Your engine may need to be replaced if a worn-out piston or worn-out connecting rod bearing is the source of a banging noise. Up to $1,000 can be spent on this.

In some cases, a simple tune-up or cleaning of the pistons or valves may be all that is required to fix your car’s squealing sounds. In most cases, this will run you anything from $100 to $300. If you use an effective carbon cleaner, you can save a lot of money.

e) How long will an engine last with a rod knock?

A rod knocking engine might run for up to six months before it blows up. However, operating an engine with a rod knock is not recommended since it might cause more engine damage and reduce its lifespan. A technician should be consulted if you hear a rattling sound coming from your vehicle.

f) Does rod knock come and go?

In the event that your engine sustains any physical damage, rod knock will always be present to some degree. You are more likely to have engine damage if you hear it more frequently.

g) Can rod knock be eliminated?

In most circumstances, the only way to completely remove rod knock is to replace the faulty components. The knocking can be minimized, but there are ways to do it. Your engine is one of the most critical things you can do to ensure its long-term health.

Your oil and gasoline quality should also be checked to ensure they are up to pace. Changing the oil or adding an oil additive can also help eliminate rod knock.

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