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i just noticed a hissing sound two nights ago. i can hear it while driving. i opened the hood and it seems to be coming from near or behind the throttle body. i don't see anything unattached and i don't see any cracked hoses. any ideas? the sound seems to go away when the engine is under stress (don't know exactly how to explain what i mean) it is not just with acceleration, the sound decreases or goes away when i push the gas lightly and the engine bogs a slight bit before shifting. just before shifting the sound seemingly goes away. i hope this makes sense.

no warning lights. no change in how the car drives. i did notice a decrease in mpg on my last tank, but i didn't notice the sound then.

any help is always greatly appreciated. thanks

seth
 

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Sounds like the vacuum line to the EGR or to the EVR, I don't know where the EVR is on a 95.
 

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Discussion Starter #7
Do you know the name of the plug carlosthecat or anyone else? i don't know what any of these parts look like or where they are so i have to research them. thanks again.

seth
 

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You have a vac leak. Look hard at that tee in the pic above. Might as well replace it if original. It will get worse and then you will have stalling problems and throw a code.
 

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Also look at those green and red smaller hard vacuum lines as shown in the wide picture, that is the EVR. If it is happening at a certain engine speed than it might be something that is dependant on speed to provide vacuum.
 

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you were correct carlosthecat. it was the t-piece. replaced it .. no hissing. thanks again.

seth

You’re welcome, that’s good news. I replaced mine a couple of months ago, I figured what the heck Ill take a pro active approach for the first time and when I took it off the bottom inlet of the T was smashed in almost like it had warped.
 

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WOT Junkie and avid corn burner
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I have a similar problem with my '96 right now. It just started tonight. Loud hissing coming from behind the throttle body. I checked all of the vacuum fittings on the intake elbow and no leaks that i could find. I can unplug the connector to the IAC and plug the inlet with my finger and the motor still runs. Throttle is closed. Sprayed MAF cleaner all over the intake manifold and no increase in RPM. I'm throwing no codes. STFT and LTFT are all negative in the single digit percentages for both banks. I don't know what the heck is going on. Maybe it's time I finally do that PI intake swap, eh? lol

Video of my vacuum test.
http://youtu.be/UhTuoeaU0FM

another vid. In park, idling.
http://youtu.be/Bna2EPTnVz4

short drive. WOT 1-2
http://youtu.be/F8ri-X4t63A
 

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WOT Junkie and avid corn burner
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why you spraying maf cleaner all over the intake manifold?
It's flammable. If it gets sucked in and RPM's increase, I find the leak. It was all I had at the moment. I sprayed into the IAC and RPM's increased a little bit.

Edit: The hissing sounds like it is coming from inside the intake manifold, behind the throttle body, just for clarification. It's doing it this morning too, not that it makes a difference.

Edit: I capped off every manifold vacuum source and I still get the hissing to the same extent. I take off the tube to the IAC and plug it with my finger, IAC has suction, hissing still there, engine still running. Throttle body has never been messed with. I'm thinking it may be a cracked intake manifold. I'm at my wit's end on this.
 

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WOT Junkie and avid corn burner
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Well, any ideas as to what it may have been? The hissing noise coming from within the intake manifold? I looked at my old intake manifold and could not find any cracks that I could see on the outside. I did notice that coolant did leak out to the intake manifold gasket mating surface with the cylinder head and intake port closest to where the heater tube nipple was leaking on the passenger side.
 

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I've had leaks on all the cars at the intakes.

The fix has been a pi intake swap. Replacing gaskets didn't help because of the manifold.

The one on Lazarus shrank kinda, leaking all along the pass side.

You can be leaking only air, and not water.

MaF cleaner won't work if the hole is too big; use starter fluid, it is more sensitive. And dangerous, lol.

Putting A/F up on the computer from the xcal while you're doing it helps.
 
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