What Causes Engine Knock, And How Can I Prevent It?

Engine knock is a term used to describe two types of odd sounds in gasoline engines. There are strong knock, which can cause permanent damage, and weak knock. Weak knock isn't much of a problem, it can even increase flame speeds (good thing) in the engine.

Strong knock sounds like a rattling noise. It's the same sort of noise you'd hear if driving too slow in a high gear, but the point is that you hear rattling when you shouldn't; when you are going fast enough for the gear.

Strong knock happens when fuel ignites irregularly and prematurely, causing erratic pressure differentials within the combusion chambre. Small explosions literally result potentially damaging the pistons and other parts of the engine.

To avoid knock:

Use the right octane fuel for that engine (not too low).

Let the car engine warm up before driving, and certainly don't push the engine hard when it's still cold.

Do not use a Turbochargers on engines not designed for them.

Some engines are poorly designed and will develop knock due to their own structural problems.

Related to that, knock may occur because the engine is getting too hot.

After I change the oil on my car the engine knock . But only at idle speed what you think is the best solution.

I hear a rattling sound when starting engine and when engine is idling, I see metal fragiments left in the draining tray everytime I drain oil. What seems to be the problem?

That is a very broad question. First thing could be the Rod bearings. Second it could have a cracked flex plate or commonly known as a flywheel.

1. MY cars engine is knocking in while shifting from 2nd to 3rd gear.
2. Its cam sprocket was found broken when engie was opened.
3. After changig the sprocket also, the problem is same.
4. Checked ECM, Fuel PUMP, TIMING,
plz suggest

Depends on the knock.

A light knocking sound only during acceleration would be combustion knock. This is caused by incorrect ignition timing or low octane fuel or both.

A dull thud like knocking sound that seems to go away at higher speeds would be worn out internal engine parts like bearings. This is more serious as the parts could break if this goes on for too long.

Low grade fuel or timing is off

Theres several different things a bad bearing low oil burnt oil that needs to be changed