I have a 96 GT, pretty much stock. The only power plant modification that has been done is had a BBK Cold Air Kit installed. Currently when the car is running there is a very loud hissing noise coming from the engine. I have checked the PCV valve hose which runs to the intake, the vacuum reservoir under the right front fender, remounted the intake and still there is this very noticeable and very loud hissing noise. The noise does not change pitch or intensity as the engine turns higher RPMs. I'm at a complete loss as to what this is coming from. Any ideas or suggestions would be greatly appreciated.
To this i could not tell you. The kit was already installed on the car when I bought it. I have taken it off and reinstalled it myself without any change in the noise.
A trick we use everyday in the shop to find intake leaks is to start the vehicle get a can of throttle body /carb cleaner (must be 02 sensor safe) and slowly start spraying over the areas of the intake that could be possibly leaking (around the gaskets, vacume lines, esp vacume line connection) you will notice the idle of the vehicle change when you find the leak, to make 100% for sure stop spraying let it start ideling as normal then just hit the spot again where you think the leak is, if it acts up again then theres your leak. Hope this helps.
the carb cleaner trick works but anyway i had this same problem with my 96 and couldnt figure it out for anything.well i popped the upper intake plenum off,no big deal 4 bolts and on the underside of it there is some sort of screw/plug the screws in there near where the throttle body mounts and mine was backing out for some reason,screwed it in tight and never had the problem again.check into it.i couldnt find mine with the carb cleaner though.
