I noticed this hissing sound on the car when start it up and am idling. Any idea what the problem could be?
It even continues for a bit while I'm driving.

 

If you have an aftermarket intake, that could be it, most namely CAI or hybrid.

 

It could be:

1) An aftermarket intake

2) Some cars make the hissing noise if you have the ac or heat on at the lowest setting

3) Or the snake under you seat

 

Or it could be an exhaust leak.

 

Thanks all,

I don't have an aftermarket intake. But what I do notice is that when I'm in a driveway or garage it sounds like its coming from underneath the car. What are the symptonms of an exhaust leak?

 

A hissing sound coming from underneath the car.

 

start your car and then get underneath it, have someone put their foot over your tailpipe to create back pressure. Listen to determine if it is leaking from the exhaust somewhere else. Also, look for black soot (or discoloration) on your exhaust piping. I would just hope it's the fuel pump you're hearing. Good luck.