Weird Hissing Sound from Engine...
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Junior Member
Joined: Jul 2000
Posts: 29
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From: Central Mass
Weird Hissing Sound from Engine...
I have an 87 Formula with the LG4 Carburated engine, and 5spd trans. At only part throttle, and only in 4th or 5th gear, there is a high pitched hissing/whistling sound coming from under the hood, and it sounds like it is probably on the upper left side or center (near carb). It increases in loudness with more gas, but then goes away when I reach 1/3 or 1/2 throttle. is this some sort of a vacuum leak, or something more serious? Thanks,
Steve
Steve
Member
Joined: Jul 1999
Posts: 339
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From: Georgetown, MA
Sounds exactly like a vacuum leak. Look for open ports, dry rotted lines, and intake leaks. Since it's by the carb, look for a leaky carb gasket too.
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-Jason M. 1991 Camaro Z28
"Its Blue."
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-Jason M. 1991 Camaro Z28
"Its Blue."
Member
Joined: Apr 2000
Posts: 213
Likes: 0
From: Ok, USA
I am having the same problem on my TPI motor and it is a vacum line.
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TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph
"Speed kills, wanna live forever, drive a Ford."
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TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph
"Speed kills, wanna live forever, drive a Ford."
Junior Member
Joined: Jul 1999
Posts: 78
Likes: 0
From: Bootiful BC, Canada
My carbed LG4 just started doing the same thing. It's a high pitched sound at idle and when I hit the gas the frequency (pitch)drops (less vacuum?). It only seems to happen when the engine is cold (thermac routing?). I gave it a visual but didn't find anything.
Supreme Member
Joined: Jan 2000
Posts: 1,123
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From: jeff NY usa
Car: 86 Z28
Engine: 350
Transmission: W/C T-5
Axle/Gears: 9 BOLT 3.45 POSI
Check to see if your airpump vavles are leaking.
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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.
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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.
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