Whistle sound after idle adjustment - normal???
 

Howdy guys,

This is a follow up to earlier posts about idle adjustment, and I thought I would start a new discussion to get better visibility to this iquestion.


I have an 85 Carrera and I've gone through the idle adjustments as described in other threads here (using the jumper, yada, yada, yada). I ended up turning the air bypass/idle adjustment screw in a ways from the prior setting and that has given me a pretty stable idle just below 800 RPM with the jumper removed, and this seems to have eliminated an annoying idle bound/surging when warm, and the cold idle is okay - so that part seems good.

Here's the strange part. At this new setting, I hear a high pitch "whistle" sound when accelerating through the 2500 - 3200 RPM range, and that wasn't there before. It's hard to describe the sound but it reminds me of the sound of the turbo spooling up in my Saab.....or the sound of a hearing aide that has the volume set wrong and has feed back.

I don't hear it when cruising with the engine in that RPM range, it seems to only happen when accelerating somewhat aggressively. This makes me think it is just a whistle effect as the air is moving more rapidly through the internal passageways. But on the other hand, part of me is wondering if some electrical component is experiencing some sort of feedback or ???? that is making the sound

I can't tell where the sound is coming from since I have to be driving the car for it to occur, so I'm hoping others here had experienced this and have suggestions about what to do about it - if anything.

By the way, I am using a K&N air filter if that is important.

Thanks for the help!

I got this whistle too around the same RPM when I had first installed a K&N filter. Regular filter didn't whistle. I cut out the airbox lid and now the K&N no longer whistles, it just screams. In a nice way.

Whistle
 

I had the same whistle after I adjusted my air screw out some. I ended up replacing both the screw and the o-ring (from our host), and cleaning the housing. Maybe your o-ring was torn or damaged when you turned the screw in.

With a K&N, annoying but normal. think of it as a want to be turbo SmileWavy

I replaced mine with a new oem screw and oring, it did not help until I switched back to oem filter and box, of course with box cover mod :D

I assume you are stock chip, if so the rpms are at 780, as you wrote "right below 800RPMs"

j

Avoid K&N and FRAM crap like my ex wife......

OMG M, you kill me brother SmileWavy

I changed out my adjustment screw and o-ring, as well,...but it had nothing to do with whistling.

I guess you could set it back to where it was and see if it goes away?

BEST!

Doyle

I installed an open air box lid last year. That gave me the whistle or at least let it be heard. A chip change and plenty of adjustment of the idle and the whistle was always there. Few months ago I went through and replaced/reconditioned/adjusted every gasket and hose from the heads out to the airbox. The project started as corrected intake manifold air leak but as I was in there I check and corrected every hose/line/connection I could find. I don't have a whistle anymore. -J

Can someone provide me the part # for the idle screw and o-ring so I can order it from Pelican? Thanks!

Update -

Last weekend I pulled the K&N air filter, and replaced it with the stock one - - - no more whistle, so I am going to leave that one in.

Also, I ordered the adjustment screw (which comes with the new o-ring seal) from our host and I plan to install it this weekend.

For reference, here are the part numbers for the screw and cap

adjustment screw: 930-110-919-00-OEM
cap for above screw: 930-110-520-00-OEM