Car is making a hissing noise during acceleration.

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I've recently got this car and I just noticed a quiet hissing noise whenever I accelerate. It sounds like it's coming from under the hood and I can only hear it with my windows opened.

My car has 232000 miles.
My car has an automatic transmission.

Hi There, There are many things that could be caused by this, however a a common symptom of a vacuum leak is a hissing that will become more noticeable during acceleration as you describe. High idle speeds or in some cases rough idle and stalling are also 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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