Simon wrote:

> My car (2001 Chev Impala) makes a kind of hissing noise while accelerating
> (together with loss of acceleration power and worse gas mileage). It's
> getting louder and louder. Many advices from the groups suggest it must be
> from Catalytic Converter. But my dealer says it's not the converter based on
> their test, and it's normal!!!!!!
> The cat converter seems located in the middle part of the bottom. To be sure
> it's the converter, can I do this way:
> - get one person press gas pedal when the other foot on brake,
> - get my ears to the ground close to the converter to listen........
>
> If it's workable, could cause any damage to the car?

In my experience, catalytic converters don't make a hissing noise ... or
any noise at all for that matter. If you hear a hissing noise, it's
probably something else ... like a vacuum leak or something. Pressing
the gas and the brake at the same time will burn something up ...
transmission, brakes or tires... or some combination of all 3.