Annoying whistle when idle..
 

My 1987 porsche 911 is a delight to drive and care for but I can not find the source of an annoying whistle when the engine idles…it disappears when you drive.
Any suggestions?

It sounds like the aux air valve might not be closing all the way and leaving a small gap when its closed. Or supposed to be closed. Like blowing a blade of grass between you palms.
The shut off lever is able to vibrate alittle.
Try pinching off the hose and see if it goes away.

The 3.2 doesn't use a Aux air valve. There is an item called the additional air valve near the oil fill neck that will rattle when cold.

The intake runners can whistle when leaking, although I'm not sure why it would only occur when at idle. Checking to make sure all the nuts are snug would be a good first step.

Is your car new to you? If so, a 911s cooling fan can make a whine / whistle noise at idle. If you really want to know, remove the fan belt and start the motor and see if it doesn't go away. Don't run it long though without the fan moving air.

Sorry did not look at the year.Ignore

Are you still using the standard air filter?

My '86 has a cone air filter behind a hotwire afm and I can hear a whistle at idle. It's my understanding that what I am hearing is the air squeezing by the closed throttle plate -- when the throttle opens, the whistle goes away. I suspect that the standard airbox hides this whistle.

The o-ring on the idle speed adjustment can dry out. Easy to test, just press on it while running and u'll know.

Thanks guys for the responses, will follow up...

How easy is it to change this O-ring?

Funny this should be mentioned,..as I attempted adjustment of base idle and the damned thing hissed at me,...very briefly,..(and not easily repeatable)...I left it alone (cal'd) ,..but suspected something "in" there was amiss...maybe the very part you mention?

Doyle

+1 on Chris' sugestion about the intake runners. Make sure they are snugged down. If that's it, the whistling will stop as soon as you snug the offending one down.

+1 on Idle Adjustment screw O-ring.

To test, at idle lift the lid and wiggle the screw, if loose it will whistle.

Does it have an air pump for smog?

You can take a hose about three feet long and put it to your ear and probe around for the location of the noise.

so, per the above, looks like my idle adujstment screw o ring is leaking/whistling. I see the idle adjustment screw on pelican (Pelican Parts - Product Information: 930-110-919-00-OEM) but no o-ring. What to get?

Thx, darrin

I'm gonna' check the factory manual on this,..I think I've the same issue on my '89....at least that o-ring is worn..

Doyle

thanks! -- on mine, turning the adjustment screw less than 1/4 turn has (temporarily?) silenced the whistle