What Causes Abnormal Noises During Cold Engine Start?

[Randy]

Here are several reasons why abnormal noises may occur during a cold engine start: 1. Inappropriate engine oil. If the oil viscosity is too high, it can lead to insufficient lubrication during engine operation, causing friction and resulting in abnormal noises. Many car owners experience this issue after switching to different oil during maintenance. 2. Improper engine belt tension. If the belt tension is insufficient, it can produce a sharp squeaking noise, which sounds particularly unpleasant. 3. Poor fuel quality or incorrect octane rating. When using low-quality fuel or fuel with an inappropriate octane rating, the combustion process inside the engine deteriorates, causing severe vibrations and noise. 4. External engine-related noises. If the engine mounting or interconnected external components become loose, they can also lead to abnormal noises.