Q: Hissing noise.

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my car is a bmw 320i 1988 actually.. whenever i accelerate(at low speeds).. i hear a hissing noise...note it is the same hissing noise when starting my car in the morning..i think it is a belt issue..i checked the belts, pulleys and bearings...all are fine..so i searched a bit and found out that a center bearing in the car's driveshaft may cause some hissing noise..thanks for your help

My car has 152235 miles.
My car has an automatic transmission.

This may be a sign of a vacuum leak. High idle speed, stalling and hissing sounds are common signs of a vacuum leak. When a vacuum leak is present in an engine, this causes an excessive imbalance in the air/fuel ratio which creates a loss of power and causes the motor to run at a much higher RPM as a result of the increased oxygen present in the fuel charge being injected into the motor. I would recommend having an expert from YourMechanic come to your location to diagnose your vacuum leak as these can be very difficult and time consuming to trace.

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