possible boost leak at turbo? gasket?

[silver240]

so what i have is a 1990 240sx coupe with a redtop sr20det. everything is stock except for a 3 inch cat back exhaust. during idle i hear a loud hissing sound coming from the turbo. should the turbo be making any sound at idle? also when i am not under load and i rev the motor and then let off i hear what sounds like my blow off valve opening and closing rapidly, kinda like tsh, tsh, ths, tsh. instead of just one quick woosh. is that normal. by the way it is a blitz blow off valve and it is going to atmostphere. any hwlp would be appreciated. i als have a very ruff idle. sorry for all the questions.

[HPR]

It does sound like you have a vaccuum leak somewhere if you can hear it hissing at idle. Most likely a hose that has a cut or burn somewhere on it? How does your car sound when you drive it at WOT? If it's really noisy then it would be a gasket leaking.

If it drives like **** and is loud, check your T2 gasket. If it drives ok and is loud, maybe your outlet gasket?

But from what you've described, it sounds like you're getting compressor surge. Possibly the line to your BOV is done.

[silver240]

thanks for the response. i took my car to a local porsche tuner shop that i have hook ups at and he hooked up all the different vaccuum lines to a smoke machine and we didnt see it leak through any of the lines or the gaskets. is this the best way to test it? the car runs very well. i can chirp the tires going into third which to me seems like i am putting out good power but ya its loud as hell. should i be pulling vaccuum at zero load if i rev the motor in neutral? i also noticed i have a chunk of metal missing on my blowoff right where the valve seats. i think what i need is to replace the blow off valve and start from there. what i want is a blow off that recirculates. what would you suggest

[silver240]

ok another couple of questions. should my car pull vaccuum (12-14 psi) at partial throttle under load and about (10 psi) when not under load at partial load.

[silver240]

bump still need help?

[silver240]

ok i di some more research and i think maybe its my iacv. i am going to clean it later today and re-adjust it.