Q: Bmw will not go over 20 mph

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My BMW will not go over 20 mph it happened last week while driving it automatically kicked down into a lower shift and I almost got ran off the road. A week later it's sitting in the garage with high rpm and still won't go past 20 mph when parked
My car has an automatic transmission.

This may be a sign of a vacuum leak. High idle speeds or in some cases rough idle, 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. This may also be caused by an idle control valve that may be sticking or failed due to old age or deterioration. 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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