85-86 Intake whistle?
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I have replaced all the rubber, ICV is new, both MAF o-rings and R&R'ed the intake, so it should be sealed up good.
I measured my intake vacuum, today, engine warm: ~19.5 in/mercury, dead flat. When the ICV cycles, the vacuum level dips slightly, and it whistles.
I have disconnected the crank vent system (free vent with two hoses from the tower, cam cover vents capped), and removed the venturi Y-connector, so I think the manifold vacuum may be higher than stock?
IIRC, the 85-86 ICV is different than the 87-up. It uses a stepper motor, versus a solenoid.
I measured my intake vacuum, today, engine warm: ~19.5 in/mercury, dead flat. When the ICV cycles, the vacuum level dips slightly, and it whistles.
I have disconnected the crank vent system (free vent with two hoses from the tower, cam cover vents capped), and removed the venturi Y-connector, so I think the manifold vacuum may be higher than stock?
IIRC, the 85-86 ICV is different than the 87-up. It uses a stepper motor, versus a solenoid.
Drifting
Joined: Jul 2004
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From: Davidsonville, MD
Since the majority of us buy these things used and in relatively poor operating condition, could it be an issue that the whistling is normal? Or could it be a situation where the whistling happens if the ICV/ISV isn't perfectly positioned?
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Yeah! "BDDRRR! BDDRR!" "VROOM! VROOM"
....Whatever
Mike
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Ken,
I had a problem with my intake side boxes coming loose after a few thousand miles, then I had the bright idea to tighten all of the intake manifold clamps with the car warmed up. Everything is more flexible that way and it all gets sealed much better. No more slippage. This might be the right way to do it, I just don't remember reading or hearing it anywhere.
I had a problem with my intake side boxes coming loose after a few thousand miles, then I had the bright idea to tighten all of the intake manifold clamps with the car warmed up. Everything is more flexible that way and it all gets sealed much better. No more slippage. This might be the right way to do it, I just don't remember reading or hearing it anywhere.
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928 Collector
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From: Seattle
Porsche built the air leak into the intake as a safety precaution that you might have too good a combustion ... simple routine maintenance will ensure that the whistle is maintained in pitch.
Drifting
Joined: Nov 2001
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From: zürich, switzerland
That would explain why my car drives my neighbor's dog nuts
My 928 does not whistle either - probably because it is an 82 model. I have hopes it will display other musical talents & so earn enough to cover the maintenance bills.
In hope
Marton
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From: So Cal
Ken, did you ever figure out the whistle? I cannot figure out mine. Same deal, intake refresh with new orings, intake boots, isv, etc., etc. I have fiddled with pressing on the various tubes as well. Since I saw you at SF11, I have checked and re-checked the rubber intake boots. I used a 10mm vacuum tube to my ear to try to pinpoint the whistle. It seems like it is coming from somewhere around the DS T-pipe. Thanks.
