Hey guys, my cobalt only has intake atm. On friday at night I started hearing like a hisssing sound under the car. I can only hear it when I am on gear not on N. When I go off on first I barely hear it (probably because exhaust sounds a bit loud for first), then when I hit second I start hearing it when I am accelerating. If I let go of the gas, I don't hear it anymore. I was thinking maybe exhaust leak, but I got under the car and didn't see any. I want to look at it again closely. I don't think the pipe cracked because is not really that loud. I know it must be on the exhaust because when I am passing by houses I hear the rebound louder. Anyone know what it might be???? Thanks guys, it has been really bothering me.

 

it is probably your CAI they tend to make a slight hissing noise under acceleration

 

If its the sound i think it is mine makes the exact same noise. Its only at part throttle, like -10 to -12 vac.

 

No the noise happens at all times when ur accelarating. If u stop accelarating noise goes away. It happened from one night to the other.

 

intake.... your just hearing the air whistling through the throttle body

 

Flex pipe.. I have the same prob..under eccel i here a hissing almost louder then my exhaust and SC sometimes

 

It sounds like if there was a hole in the exhaust???? Is that what u get too??? How do I fix it???

 

I am guessing I will need to buy a new down pipe then, I just want to be sure it's that that is making the noise.