engine hissing on cold start

[Kenshin X]

morning guys, on some mornings, cold starting my car, the engine gives a fairly audible hissing sound when i cold start it. doesn't happen on warm starts.

fuel injectors spraying in more fuel to start perhaps?

unfortunately it doesn't happen all the time, so i don't have a video posted up, but if one day it happens when i record it, i'll postit up to make it more clear to you guys

cheers all

Happy lifting :P

[SuperDave]

It's probably just induction noise, nothing to worry about.

[DJKOR]

No need to panic mate. What you are experiencing is the air being sucked past the small opening in the throttle body. When the engine is cold, it tends to require a little more air with the higher revs. Since your throttle stays in the same position, it needs to get this air somehow. The throttle body butterfly has a very small gap around the circumference of it in which air can be drawn through. Just like sucking air through a straw quickly, it makes noise.

If you put on a CAI or SRI, you will really hear it. 1ZZ's and 2ZZ's always surprised me with the vacuum sound they made which was usually more than other cars.

[Kenshin X]

awesome i want this sound to be louder when i accelerate! B) jk

cheers guys