Anyone seen this before? Whistling throttle body...!

[Guest]

Got an odd one for you...

Since I got it over 2 years ago, my car whistles from around the throttle body on light acceleration from 2000-4000rpm. There is no vacuum leak (confirmed by attaching a gauge to one of the vacuum hoses on engine side of throttle body and also, (with the engine off), the hissing sound of air when one of the vacuum tubes is disconnected after the car has been sitting overnight).

The whistle goes if I apply full throttle. I can even hear it when I open the engine cover and blip the throttle just lightly. I cleaned out the idle control valve today, but the whistle is still there. I have checked all the engine breather hoses & sprayed carb cleaner around every joint in the induction system repeatedly, with no effect on the idle speed, so I don't think this is an induction/vacuum leak. I even took my motorsound cover off & put the original one on, but no improvement.

Seems that a few cars have this problem going by what I've seen on the internet forums... a whistling throttle body.

Has anyone found a solution? It's driving me mad. []

By the way, my car's a 1994 normally-aspirated non-varioram, 107,000 miles & drives beautifully otherwise.

Thanks,
Roddy

 

[Guards Red]

Hi Roddy,

I take it you're not sure it's the throttle body? The alternator bearings will whine, so will the fan one when they're past their best. Perhaps it's not the induction at all?

 

[Guest]

Hi GR,

Absolutely sure - new alternator 7k ago plus I can get my ear quite close and hear it's coming from around the throttle body somewhere. Sounds just like a turbo spooling up (except I haven't got one!). Starts at about 2000rpm, goes by 2.5-3000rpm and a high-piched whistle. Vanishes when driving if I immediately take foot off throttle or floor it. I can even hear it when lightly applying throttle with engine cover open in the garage.

It's driving me mad. I'm wondering about unbolting the throttle body next and washing the plate with carb cleaner and a bottle brush. Have seen that recommended for Saabs in the past when I ran those. Wonder if I should try this next?

Help! [8|]

 

[Guest]

Apparently it could be leaking bushes on the resonance valve spindle. Will check shortly...

 

[Guards Red]

Roddy,

a mechanic's stethoscope may be worth the investment for this. You can buy one from your local toolshop for about 15 pounds. Comes with an extension probe which allows you to isolate sounds quite effectivly.

Worth a shot. One way of a quick check of the resonance flap is to check for any oil under it on the fan shroud. Most intakes have some residual oil in them and it will leak out if the bushes are worn.

Hope you get it sorted. I have a rattle that only manifests itself only when the car's moving which is slowly driving me mad.

Regards
GR