I have a 1990 LS 400 and am curious, when I open the hood and rev the engine via the throttle cable, I hear a small noise that sounds like compressed air. Does anybody think it's a leak somewhere or is this noise normal. It's like a "psssh" sound. Is this sound normal? Does anybody notice this sound? You can only hear it if the hood is open and you are listening, very close to the engine.

 

Probably a crack in the EGR pipe between the engine and firewall. you need to get a tube for your ear and block the other ear to find it--or use a mech. stethoscope with the end off so you can use just the hose.

 

thanks. . . will give it a try

 

I just took it in to a mechanic, and they said that everything checks out a-ok. Umm, I was hoping somebody could see if their car emits this noise as well? I have a feeling that it is not normal. . . it sounds pretty strange to me.

 

I've got the same car and have no such noise