1. Low oil pressure: When the engine is cold, the oil is thicker and flows more slowly, resulting in lower oil pressure. This can cause the engine components to knock as they don't receive adequate lubrication.
2. Worn engine components: As engine components wear out, they can develop clearances that allow them to knock against each other. This is especially noticeable when the engine is cold and the metal components have not yet expanded to fill these clearances. Common worn components that can cause knocking include piston rings, piston skirts, connecting rod bearings, and main bearings.
3. Carbon deposits: Carbon deposits can build up on the piston tops, cylinder heads, and valves over time. These deposits can cause the engine to run hotter than normal and can also lead to knocking sounds as the carbon deposits interfere with the smooth operation of the engine components.
4. Faulty ignition timing: Incorrect ignition timing can cause the fuel mixture to ignite too early or too late, resulting in a knocking sound. This is more likely to occur when the engine is cold because the air-fuel mixture is denser and more difficult to ignite.
5. Faulty fuel injector: A faulty fuel injector can deliver too much or too little fuel to the engine, causing a knocking sound. This is more likely to occur when the engine is cold because the fuel does not vaporize as easily and can pool in the cylinders.
