Why does the car make a hissing sound when starting cold?

[LaHarley]

When a car makes a hissing sound during a cold start, it is usually due to poor combustion in the cylinders. Poor combustion results in insufficient power output, causing the car to shake. If the engine makes a hissing sound during a cold start but quiets down after about a minute, and the sound is much quieter during a hot start, this is considered normal. This happens because after the car is parked, the engine oil automatically flows back into the oil pan. During a cold start the next day, the oil slowly returns from the oil pan to the vicinity of the cylinder head. In a hot start, the engine oil is already in place, providing good lubrication and sealing, which naturally results in a quieter sound. Therefore, the sound during a cold start is louder, but it should not last long. If the engine continues to roar for an extended period, it is advisable to have it checked at a repair station as soon as possible.