What is knocking of engine?

Engine knocking is a term used to describe a particular type of abnormal noise that can occur in internal combustion engines. It is characterized by a rapid, metallic tapping or pounding sound that is often heard from the engine compartment. Knocking can be caused by several different factors, but it is typically associated with problems related to the engine's combustion process or mechanical components.

Here are some of the common causes of engine knocking:

1. Insufficient Fuel Octane: When fuel with an octane rating lower than what the engine requires is used, it can cause the fuel to ignite too early during the compression stroke, leading to a knocking sound. This is known as pre-ignition or detonation.

2. Carbon Buildup: Over time, carbon deposits can accumulate on the piston crowns, cylinder head, and valves, causing hot spots that can lead to pre-ignition and knocking.

3. Engine Wear: Excessive wear on the engine's components, such as piston rings, bearings, or camshaft, can cause increased clearance between moving parts, resulting in knocking sounds.

4. Faulty Sensors or Ignition Timing: Improper ignition timing or malfunctioning sensors, such as the knock sensor or oxygen sensor, can cause the engine to operate outside of its optimal parameters and lead to knocking.

5. Low Oil Pressure: Insufficient oil pressure can cause inadequate lubrication of the engine's components, leading to increased wear and potential knocking sounds.

6. Insufficient Cooling: Overheating can cause engine components to expand, leading to increased clearances and knocking noises.

7. Damaged Piston Rings: Worn or damaged piston rings can allow excessive blow-by of combustion gases, resulting in a knocking sound.

8. Loose Connecting Rod Bolts: Excessive clearance in the connecting rod bearings can cause the connecting rods to knock against the crankshaft.

9. Bent Valves: Bent or damaged valves can lead to improper sealing of the combustion chamber and knocking noises.

10. Improperly Torqued Head Bolts: If the head bolts that hold the cylinder head in place are not properly tightened, it can cause the cylinder head to lift slightly, leading to knocking sounds.

Knocking is generally a sign of a potential engine problem and should be addressed promptly. Ignoring knocking sounds for an extended period can lead to more severe engine damage and costly repairs. If you hear knocking noises coming from your engine, it is recommended to have the vehicle inspected by a qualified mechanic as soon as possible to identify and address the underlying issue.