Attention! If you have the slightest doubt about the results of your self-diagnosis, get out the towing rope. A major repair to a damaged engine will cost more than a towing service.
Knocking of main bearings - very dangerous; stop the engine immediately, you will have to be towed to a car service center or garage. Low pitched knock. It can be heard in the lower part of the crankcase, and noticeably increases under load and with increasing rotation speed. Often its appearance is accompanied by a drop in oil pressure (the oil pressure warning light is on almost constantly).
Knocking of connecting rod bearings - very dangerous; stop the engine immediately, you will have to be towed to a car service center or garage. The sound is rhythmic, ringing, metallic, medium tone. Increases significantly with increasing load and disappears completely when the spark plug is disconnected.
Knocking of piston pins - dangerous; without putting any strain on the engine, you can drive to the car service center or garage on your own. Rhythmic, high-pitched with a sharp metallic tint, audible in all engine operating modes and intensifying with increasing engine load. Disappears completely when the spark plug is disconnected.
Knocking of worn pistons and cylinders - not dangerous; without putting too much strain on the engine, you can drive to the car service center or garage on your own. A sound reminiscent of the clatter of clay pottery. It is especially noticeable on a cold engine, and as it warms up it decreases or disappears.
Valve knocking - not dangerous; you can get to the car service center or garage yourself. A metallic knock against the background of a general dull noise. It can be clearly heard at low and medium crankshaft speeds from the cylinder head side above the valve locations.
[Article based on data from the website www.LadaMan.ru]
Detonation knocks - are dangerous; however, by avoiding heavy engine loads, you can drive to a car service center or garage on your own. A loud metallic knocking sound that usually occurs when the car accelerates. The cause is a faulty knock sensor, use of low-octane fuel, engine overload due to too early engagement of a higher gear, significant carbon formation in the combustion chambers. It is necessary to select the correct gear depending on driving conditions, fill up with gasoline with an octane rating recommended by the vehicle manufacturer, check the knock sensor, and use a special fuel additive to remove carbon deposits on valves and in combustion chambers.