OK I'm about to go take a closer look and find out where the noise is coming from but what I know so far is it only comes on after I put the key in the ignition and power is sent to the car. The hissing sounds like air or gas or something is being leaked out or pushed out as it is fairly audible. It's coming from somewhere close tot the center of the engine.

Anyway I'm going to go have a look at it with a flash light so I can actually see where it's coming from.

The car is idling hard and almost always dies after being left to it's self for more than 20 seconds if that. It gets down to about a .5 rpm and just struggles and then shuts down.

But does anyone know what this might be just off hand?

Thank you in advance for your replies, everyone here is so helpful. :classic:

-Eli

Oh by the way it's a 1978 280z.

So let me understand... it makes the hissing sound even when the car is not running, just with the power on. If thats the case, it sounds like you have a leak somewhere in the fuel system. I think 280Z's have an electric fuel pump.

Normally a hissing would be attributed to a vacuum leak, but if the engine is not running, thats a tough one.

The engine has to be running if it won't idle properly ;-)

You have a broken vacuum line, INK. One of those squiggly black hoses covering the top of your engine. Another issue here is that if one of the vacuum lines is dried out, leaking and/or broken, chances are that the rest are soon to follow. In other words, replace them all. I don't know much about 280Z fuel systems, sorry. A service or repair manual would tell you what is what.

Well I was saying that it hisses when only the power is supplied to the engine and simply noting that it idles rough WHEN i start it.

Yeah i was trying to find where it was coming from and I couldn't really pin point it other than it was near the middle of the engine, I'm going to ****ing look again and see what I can tell but it probably doesn't help that I've never worked on a car in my life other than the simple stuff like oil changes and brake pad replacements.

If it is a vacuum line, is that expensive to replace?

Is it a pain in the arse or easy?

So let me understand... it makes the hissing sound even when the car is not running, just with the power on. If thats the case, it sounds like you have a leak somewhere in the fuel system. I think 280Z's have an electric fuel pump.

Normally a hissing would be attributed to a vacuum leak, but if the engine is not running, thats a tough one.

Yeah the engine is NOT running, when the hissing is heard.

Vacuum lines are easy to swap out. It's just a rubber line that goes from A to B. The only issues you may have are easy to avoid: Don't pull all the hoses off at the same time, tempting as that may be. Just do them one at a time, that way you'll know that they are all in the correct place. Second is to get the right diameter hoses, and cut them to the proper length.

Hmmm... you got me stumped.

Nooooo!!!! :'(

Not running when noise is heard...

That might lead me to suggest checking your fuel lines, as the pump does get juice when the key is turned. If there's a leak, you'd hopefully hear it, but most likely smell it...

that's what I was thinking, but didn't really smell anything, although from sniffing around it I do feel kind of light headed.

The sounds seems to be coming from around or very close to the fuel filter.