1988/328 hissing noise

Is your neighor's cat missing, by chance?

 

Does it go away after a few seconds, or few minutes, or never?

One thing you can try is using a ~3' piece of hose held up to one ear as a crude stethoscope to try to localize where the sound is coming from.

 

Get a can of carb cleaner and spray a little at each vacuum fitting, one at a time, it there's a leak it will drawn it in and the engine rpm will change.

 

Smoke test it. It will show up in 30 seconds.

 

can your explain this please. I have no idea what you mean by that. Maybe it’s a translation misinterpretation.

 

There are "smoke machines" made for this purpose.

In the old days mechanics used cigars or cigarettes to 'generate' smoke. They would move the cigar/cigarette close to the various fittings/hoses and observe where the smoke was sucked in. Back then, almost every man (and boy) smoked so pretty much everyone had a "smoke machine" with them at all times! Handy for checking vacuum leaks, indoor draft leaks (door/window seals), etc!

Ah...the good old days!

 

Cuban Havana's these days if u own a ferrari. If that does not stop the engine nothing will

 

Well, the way I use the smoke maker is to attach the smoking business end to a hose on the plenum and see where the smoke comes out and that is the leak.

I save my Montecristo #1 for a good scotch, a good friend, and a reason to celebrate.

 

The cigar thing works. I gave up on flammable sprays in engine compartments when coil over spark plugs came around. Can you say "fire"?

I rubber band a nitrile glove over air intake(s) and use a vacuum take off (like the one feeding the brake booster) as a point to attach a 3 ft hose. Blow cigar smoke into the hose a few times and you will notice the gloves starting to inflate. Put your finger over the hose end and start looking for traces of smoke from places that should be sealed. A Partagas Series D No 4 works nicely