This is vacuum related and I just can't pinpoint the source, and it goes away completely under low vacuum/acceleration but as soon as I release the pedal it comes back and it's constant. I have checked all vacuum circuits and failed to find any leaking. I am suspicious of the intake "box" over the throttle body but don't have a clue where/how to check that, can anyone help on this? FWIW, this issue has been on going since I got the vic but was more apparent after I replaced all plugs, ignition wires, dizzy cap and rotor. Truck runs great, no SES illuminated, no driveability issues at all.
Mystery whirl/whine/houl under dash...
- Thread starter zomeizter
- Start date
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SunlitComet
OBS Jedi-Do Good
if it from under the dash it could be the brake booster leaking.
well ma man, that's the first thing I checked and it is good, I pinched the vacuum supply to it and no change was noticed. Upon closer examination, I believe it is in the throttle body area inside the intake; I popped the hood and could hear it the loudest when I "hovered" on top of the engine. Like I mentioned earlier, as soon as vacuum drops, it goes away. PO did the intake gaskets before, guess ima have to tear into it sometime, maybe when the poppet valves crap out...for now, I will keep the radio on at all times 
SunlitComet
OBS Jedi-Do Good
is the clip on the intake ducting intact and gripping the tb and is the wing nut holding the setup down?
You're talking about the metal clip facing forward? As far as intact goes, no it is not, it is actually a bit loose but there are no leaks at the neck of the TB at all. The wing nut is there and keeps it all together...
SunlitComet
OBS Jedi-Do Good
you can carefully spray some starting fluid around the intake manifold system to see if you get a rise out of the engine directing you to a possible leak.
If a leak exists, this would create a lean condition triggering a DTC, but this is not the case, or at least it doesn't behave that way. No codes are stored and all parameters show nominal on the scanner. I will dive in again tomorrow after work and once it gets its scheduled wheel alignment...steering wheel has been at the wrong position for way too long I will report findings, thank you sir.
I will report findings, thank you sir.
SunlitComet
OBS Jedi-Do Good
well you would be surprised how much a leak can get by with out triggering a code. when my booster was failing it would sometimes leak enough air as if i pull the pcv line off. it would wander in and out and not one code ever despite the fact that the engine was near stalling and surging.
well, it's too damn windy outside and the vette is taking up all the room in the garage so I cannot check it further until this 4-day sandstorm ceases...on a different note, I couldn't get an alignment done for several reasons: both lower ball joints are completely shot, as well as the idler arm. Thanks for the input Sunlit, I will hunt the intake issue soon and get back with results, hasta...
I sprayed a couple cans of carb cleaner around the intake and everything near by, could not locate a vacuum leak whatsoever...but I found a strange thing: I serviced the tranny filter and pan gasket and refilled with synthetic DEX/Merc fluid. I also changed the engine oil and filter, when I started the truck after all fluids were replenished, I could no longer hear the mysterious sound, what the hell!!?
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