I have an 02 neon se i just got with 65,000 miles stock. When i floor it and it gets to a certain RPM theres a hissing sound that comes from the motor and then when it shifts (its automatic) and the RPM's drop, it stops then starts again when it gets to the same RPM until it shifts. anyone know what this could be?

 

What RPM does this "hissing" sound start at?

 

I think its starts around 5 or 6.

 

mine does the same thing but not at 5 or 6 RPM.... more like 2-4 for me... i think its comming from the CAI on mine.... the engine pulling in all that air i think.... b/c its when i press the pedal to a certain point but then it stops..... so it might be the TB position and the air passing through it....? idk just my thought... and what are you doin beatin on that poor auto tranny... 5-6 RPM.... humph!

 

That's important here. Do you have a CAI? The CAI makes some weird noises when the throttle plate is almost completely closed. Izero is correct about that. At 5-6 at WOT the intake shouldn't hiss. CAI will rohr. It may be a vacuum line that leaking or an exhaust leak. Just guessing.

 

maybe a vacuum leak because when im sitting at a red light my rpm's drop and the car shakes but if i turn the wheel to the side then back staright the rpm's jump back to normal, and those no CAI on it (yet).

 

Possible power steering rack valve sticking.

 

just throwing ideas out.
But can you reve the egnine with your head under the hood?.
See if you can locate the rough source of the hiss??