1. Worn piston rings: Worn piston rings are a common cause of low compression. When the piston rings are worn, they can no longer properly seal the combustion chamber, which allows air and fuel to leak past them. This results in a loss of compression.
2. Cylinder head gasket: A blown cylinder head gasket is another possible cause of low compression. When the cylinder head gasket is blown, it allows air and fuel to leak between the cylinder head and the engine block. This results in a loss of compression.
3. Valve seal: If the valve seals in the cylinder head are worn or damaged, it can also result in poor compression. The valve seals help to seal the air/fuel mixture inside the combustion chamber when both of these components fails it lets compression gases pass by them
4. Damaged Cylinder Bore: A damaged cylinder bore can lead to lower compression in the affected cylinders because of poor sealing of piston rings to the worn bores of the cylinder which allows combustion gases to past by, reducing compression
* To determine the exact cause, further diagnosis, such as a leak-down test, would be necessary to identify whether the issue is with the piston rings, cylinder head gasket, valve seals, or cylinder bore.
