Why Car Engine Knock on Startup then Goes Away?

Engine knocking on startup and then going away can happen for a number of reasons. If you are hearing the noise, but it goes away after warming up your vehicle for a few minutes, there is likely nothing serious to be concerned with your engine at all!

engine knock on startup then goes away

However, the engine knock on startup can be caused due to piston slap, worn-out engine parts, sticky lifter, worn-out bearing, carbon buildup, etc. that may become a significant issue down the line.

Whatever may be the reason, we’ll discuss them in detail in the following sections so that you get a clear picture of what’s going on in the car. And provide you with details on the fix and how to prevent this from happening in the future. Stay with us!

Piston Slap

Piston slap is a normal engine noise that occurs on starting the engine or accelerating. Piston knock can be caused due to engine piston moving from side-to-side during engine rotation, as it tends to move around more when cold.

Once you start your vehicle and let it heat up for a few minutes, then there’s very little chance of engine piston slap. Although not a big problem yet, but piston slaps happen due to either bad timing of spark plugs or worn-out pistons.

Worn-out engine parts

Worn engine parts can be another reason for engine knock noise on startup. Most often, it happens due to worn-out engine rings and/or engine bearings which let metal particles flow into the engine oil, leading to the formation of sludge in the engine.

It’s high time that you take your car for immediate service if you hear any unusual or weird engine noise that doesn’t go away after a few minutes. If it does go away, we still recommend you to be cautious and have it checked up so that it lasts long.

Sticky engine lifters

If engine oil is not reaching the engine parts properly, it can lead to sticky engine lifter and worn-out engine seals. It may cause piston slap or even engine knock on startup as well.

The best solution for this problem would be changing your vehicle’s engine oil regularly, working with an engine oil additive to protect engine parts, and getting your engine checked at regular intervals.

Worn-out bearing

Bearings are rotating engine components that allow smooth movement of the engine parts in the engine block.

If these bearings become worn out due to wear or tear, it can lead to piston slap or even knocking on engine startup.

Carbon buildup on engine

If engine oil is reaching the engine parts in wrong quantities, or if the car is old, it can cause carbon build-up over time which will lead to engine knocking or engine piston slap while turning on your vehicle.

How to Fix this?

If engine knock on startup goes away after a few minutes of warming up, it’s most often nothing to be worried about particularly if you hear the noise only once in a while and don’t feel any other problems with your vehicle such as engine oil leakage or engine overheating.

However, it’s a sign that there are some issues inside the engine which may deteriorate soon. To prevent that from happening, you should follow the guide below and use performance-enhancing engine oil treatment additives like this one-

How to Prevent Engine Knock On Startup that Goes Away?

Engine noise can be caused due to engine piston slap or wear and tear of engine parts. If you are hearing engine knocking sound on startup, it’s time that you take your car for a check-up at a nearby auto repair shop because regular engine knocking can be a sign of serious engine damage if the problem is not diagnosed properly in time!

Apart from the things we have mentioned above, you should follow these tips to prevent your engine from malfunctioning-

Use Good Quality Engine Oil Regularly

Using engine oil that is of good quality will reduce engine wear and tear. When you start your car, it gets hot fast, which means engine parts expand rapidly causing friction between metal surfaces – this can lead to engine damage if proper lubrication isn’t ensured.

Engine Oil additives help improve engine performance by reducing heat generation and increasing the life of engine parts. Diesel engine oil additives are used to clean up engine wear particles, stop engine knock on startup, and improve fuel economy by removing carbon deposits from engine valves, pistons, and combustion chambers.

So make sure that you check your owner’s manual for the recommended viscosity grade of engine oil or consult an expert for advice before filling up the engine with engine oil.

Work With Engine Tuning Experts Regularly to Adjust Engines Properly for Improved Performance, Efficiency, and Reliability

Proper engine tuning helps in preventing engine knock on startup by ensuring that the engine is running smoothly without any hiccups or obstacles like carbon build-up, misfiring, etc. Engine tuning experts know engine repair and engine maintenance, which is why you should not hesitate to take your engine to a trusted engine tune-up shop for engine diagnostics.

Regular engine tuning can also help in improving your car’s fuel economy and overall performance by making adjustments like adjusting the timing of spark plugs (to ensure that they fire at the right time), setting up air/fuel ratio, calibrating engine sensors, etc.

Regular Filter Change is a Must to Prevent Sludge Buildup and Clogs

Dirty engine oil leads to sludge build-up, which can affect the engine performance. Regular filter change is a must to ensure that the engine oil carries no impurities and engine parts are properly lubricated, hence ensuring smooth engine performance without any interruptions from knock on startup or other problems.

Don’t Drive Rough

For preventing engine wear and tear, avoid driving your car aggressively. Aggressive driving includes speeding or revving the engine when you are in traffic jams etc., this is because constant high speeds can cause faster wear leading to piston slap issues on startup and damage to other parts of the engine.

Never Ignore Check Engine Light

A good way to maintain the car is not to ignore any of its warning signs. Whether it’s a check engine light or sputtering, ignoring these signs can lead to many serious issues like engine damage which could’ve been easily avoided if you acted fast.

Since cold start engine noise is a sign of malfunction inside the engine (no matter how small the issue is), you should never ignore it.


Engine knock is a sign of engine malfunctioning, and it can be prevented by following the tips given in this article.

The best way to prevent engine knock on startup from occurring is to get regular engine maintenance which will help clean up carbon deposits or other debris that may have been causing your engine problems.

Regular use and change of engine oil additives help you avoid engine wear and tear as well as improve fuel efficiency through removal of carbon build-up from combustion chambers, pistons, valves, etc., hence preventing engine issues like knocking noise on startup.

However, if you’ve already experienced this and the car is old enough, several hundred thousand miles in it, the best bet is to maintain the car properly so that it doesn’t deteriorate more. But if the vehicle is new or not old enough to take it as regular wear and tear, it’s time to act fast and consult a professional to sort things out before it’s too late.

Frequently Asked Questions

Do engine knocks disappear?

In general, engine knocking will disappear as the engine reaches its optimum operating temperature. However, if there is damage to the engine’s components caused by the knocking, that damage may still be present even after the knocking has stopped.

In extreme cases, permanent damage to the engine may occur, rendering it inoperable. It is therefore important to have any knocking checked out by a mechanic as soon as possible to determine if there is any underlying damage that needs to be repaired.

Does rod knock go away when the engine warms up?

Rod knock is a type of engine knocking that is caused by a problem with the engine’s piston rods.

In most cases, the rods that are affected by this are the middle set. When you hear a knock when accelerating, it usually means there’s simple wear on the piston rod surface down to the wrist pin.

There are several types of engine knocks, but most of them are caused by an imbalance between the connecting rods and crankshaft or poor valve timing. A rod knock also referred to as “big end knock,” usually comes from misuse–typically too much camshaft duration or incorrect valve clearance.

However, some engines do produce knocks at high RPMs due to imperfections in manufacturing processes. There isn’t really any generalized correct answer for whether rod knocks go after warm-up since every engine and the fault is different.

Why does my engine knock sometimes?

There are a few reasons apart from the above-mentioned ones why your engine might knock sometimes. One possibility is that you’re running the engine too rich or too lean.

If you’re running the engine too rich, the fuel will ignite prematurely and create knocking noises. If you’re running the engine too lean, there won’t be enough fuel to keep the air/fuel mixture from detonating. This can also cause knocking noises.

How much does it cost to fix engine knock?

The cost of fixing engine knock can vary depending on the severity of the problem and the type of repair that is needed. However, on average, it costs around $500 to fix engine knock.

If your car has a knocking noise that is caused by a worn-out piston or connecting rod bearing, then you will likely need to replace the damaged parts, if not the entire engine. This can cost upwards of $1,000.

However, if your car has a knocking noise that is caused by carbon build-up on the pistons or valves, then a tune-up or cleaning might be all that is needed. This typically costs between $100 and $300. You can save a whole lot of this amount if you do it yourself with an efficient carbon cleaner.

How long will an engine last with a rod knock?

An engine with a rod knock can last up to six months before blowing out completely. However, it is not advisable to continue driving an engine with a rod knock as it can cause further damage to the engine and lessen its lifespan.

It is important to have your car inspected by a mechanic if you are experiencing a knocking noise.

Does rod knock come and go?

Rod knock may come and go, but it is always present to some degree if there is any physical damage to your engine. The more often you hear it, the worse your engine damage is likely to be.

Can rod knock be eliminated?

In most cases, rod knock cannot be eliminated altogether without replacing the affected parts.

However, there are steps that can be taken to minimize the severity of the knocking. One of the most important things you can do is to keep your engine properly tuned and well-maintained.

You should also make sure that you are using the correct grade of fuel and that your oil is up to par. Rod knock can also sometimes be reduced by changing the type of oil used or adding an oil additive.

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