Well, i was working on the car the other day, and i heard a hissing sound. So i opened my throttle blades and it got louder. My plenum had a smell of gas, but i took that as normal... The sound didn't disappear for a while, i'd say 5 - 10 minutes. What could it be?

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Gutted cat
-!AIR
-Gutted Air Boxes

 

might be normal sound or a vacuum leak does it idle and run ok?

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ICON Motorsports

1st & 3rd
MM Black Diamond 538 F&AM

 

bah, forgot to mention that the car was NOT running when i heard this, nor when i opened the blades... sorry for that misconception people. At idle it's fine.... but i'm worried that i may have something serious other than a vac. leak...

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Gutted cat
-!AIR
-Gutted Air Boxes

 

Loud hissing sound coming from the the throtle body means either bad, clogged or out of adjustment IAC. I'd go through the adjustment procedure listed on this site for the IAC and if that doesnt work, take the TB out and clean the crap out of it

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92 Z28 5.7
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Trick Flow 23° heads, Comp Cams XR270HR-10 cam, Accel intake base + ported TPI,
TES headers, Flowmaster catback, MSD ignition, #24 SVO injectors, 1LE aluminum driveshaft.

Click here to see pics of my car.
Check out our car club Truspeed
Check out the Bin Archive for all your .bin needs

 

yea but would it do that while the car is off?

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Gutted cat
-!AIR
-Gutted Air Boxes

 

Oh... so u hear that when it's not running. Well in the case you have a vaccum leak that's for sure. As you probbly already know there's vaccum stored in a little round canister behind your fender and there's also a one way check valve attached in line with the rubber hose that leaves the plenum (around the fuel pressure regulator area) and goes to that canister. If that valve is bad then air will allowed in the canister trough the plenum, so that's what that hissing might be.

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92 Z28 5.7
------------------
Trick Flow 23° heads, Comp Cams XR270HR-10 cam, Accel intake base + ported TPI,
TES headers, Flowmaster catback, MSD ignition, #24 SVO injectors, 1LE aluminum driveshaft.

Click here to see pics of my car.
Check out our car club Truspeed
Check out the Bin Archive for all your .bin needs

 

looks like i'll have to check that out later....

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Gutted cat
-!AIR
-Gutted Air Boxes