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Haunts_666

Where's my whistle.

33 posts in this topic

Recently my car has been off the road with a few issues but its back running again now all nice and fine apart from one thing. When i used to change gear i got a whistley woosh noise (excuse my terminology) but now i've only got more of a squeak now. I was wondering what cause's the sound and how do i get it back. I had to replace the ISV which i got through a wanted add but the part number was slightly rubbed off, it looks exactly the same as mine but i weren't sure if it could be this if it was the wrong one because i heard that the G60 version vents off boost (is this what causes the noise)?

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Have a look to see if your idle screw is still there!

Mine fell out before and i got a strange{stranger than normal :lol: }whistle from the engine!

You could take off the isv{just blank the hole} and take her for a spin!

If the noise is gone its your isv,if its still there then its something else!

Is she down on power?

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I don't think i explained myself right basicly it used to have a loudish whistle when i changed gear but now its really quite or barely makes any noise? I was just wondering what actually cause the whistle when changing gear? Is it boost going over a hole or something?

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It's the boost venting out the throttle body as you come off throttle

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Ahh i see, thanks. What would cause the loss of sound then because it certainly doesn't seem to have lost any boost, however i recently had to change my ISV, would this be it?

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yes it could be the isv.

When the isv bleeds it may make a whistle, your new one may just be sealing better.

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I haven't changed my ISV but I've lost my whistle. Don't know why tho, weird

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Am i right in thinking that the G60 ISV bleeds boost? Because my new one (2nd hand) the part number has lost the end code and think the G60 has a D at then end where as GTI has a C. I'm thinking if its C then it might not be venting boost.

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G60 isv vents around 1.5 bar, it also allows air in on idle

If anything putting a gti one on the is an upgrade as it will only allow air in, so you'll never loose boost through the isv.

if it's adjustable it's a g60 one

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photo0034gf.jpg

This is my ISV how would i know if its adjustable it looks completely sealed?

Going back to your earlier comment about the boost venting through the throttle body. Is there a hole or something i could check that might be blocked which is stopping the whistle?

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The g60 and 16v/8v ISVs are two different sizes. the g60 one is larger on diameter. And if you have changed it for another then I'd agree with the guys above about this being the loss of your whistle. On mine though I'm pretty sure almost all the sound comes from the throttle body where the boost return used to be. Check around there too as this should definitely still make a woosh!

Lastly, if the g60 has it's own isv I'd say this is the best one for the job. Theres a reason it does what it does.

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The g60 isv has a small hex cap grub screw on the side of the grey cylindrical part. It's normally under a blob of blue lock tight.

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Ok so now i've got the right ISV but still no whistle, would there be something around the throttle body area that might need adjusting or something? Its almost as if something isn't shutting properly because there is a faint whistle. The reason i ask is because my car went into the garage and he said he had to adjust something on the throttle body but i can't remember what?

Now i've just been looking through the Bentley manual at the idle adjustment section and the bypass valve adjustment am i reading it right that the bypass valve shouldn't open straight away because at the moment if i push the actual throttle lever open slightly the bypass valve also opens straight away?

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Hopefully he hasn't adjusted the arm that links the two butterfly flaps on the t/body (it's underneath near the connector for the fuel rail). as you open the throttle the flaps open to let the air into the inlet and close off the boost return outlet and the opposite when closing throttle.

Are you actually running a boost return pipe?

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Yeah i still have the boost return pipe. I can see the arm you mean underneath, this is it isn't it (No. 3).

pagesfrom.jpg

So am i right in that this should move at the exactly the same time as the throttle opens?

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if that bar has been adjusted or messed around with i dont think you will ever get it right again.

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Normally lots of whistling means the boost return pipe has been taken off - have you only just recently refitted it?

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Nah its always been there. If the engine was cold and you boosted enough when you changed gear and just take your foot off the clutch and not push the accelerator it would just do a long whistle for a bit but now its seems to have gone or its just a squeak. I've noticed as well recently there's a slight delay before the car accelerates if your at idle and tap the accelerator the revs drop really low. I'm thinking it might all be connected some how?

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its not down on power is it, sounds like it might of gone into limp mode and limiting boost,? just a thought hows your battery asi f this aint giving the required juice ie 12v at the fuel rail. might be worth checking.

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In regards to the return butterfly adjustment, all you have to do to set it up is get a mate (or a brick) to hold the accelerator pedal down, so the throttle plane is wide open, and then set the return butterfly to closed. When you release the acc pedal and the throttle plane is completely closed, the return butterfly should be wide open.

This is much easier to do with the throttle body off the car by the way, though it does mean you need about 5 hands to hold and adjust all the relevant bits.

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In regards to the return butterfly adjustment, all you have to do to set it up is get a mate (or a brick) to hold the accelerator pedal down, so the throttle plane is wide open, and then set the return butterfly to closed. When you release the acc pedal and the throttle plane is completely closed, the return butterfly should be wide open.

This is much easier to do with the throttle body off the car by the way, though it does mean you need about 5 hands to hold and adjust all the relevant bits.

Good to know that is ^^ B)

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Well i've checked the return valve and that seems to be ok. Maybe it is down on power i can't personally feel any difference. It seems to keep cutting out a lot lately and seems to be getting worse as if something is getting clogged up, i might have to change the fuel filter, i don't actually think i've ever changed it. Can a clogged fuel filter cause the car to stall if you push the accelerator to hard?

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have you changed the air filter at all? Paper filters damp down the charger whistle. Also a standard air box will quieten it down. For the loudest whistle you need a cone filter.

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its not down on power is it, sounds like it might of gone into limp mode and limiting boost,? just a thought hows your battery asi f this aint giving the required juice ie 12v at the fuel rail. might be worth checking.

Whats limp mode?

have you changed the air filter at all? Paper filters damp down the charger whistle. Also a standard air box will quieten it down. For the loudest whistle you need a cone filter.

I haven't changed the filter no, and it's always had a cone filter. Maybe i should give it a clean.

The stalling is gettin really bad now as well its almost every time i put the clutch in to stop. I've noticed under the bonet when you rev it, when it starts to die some times there's like a clunk sound and then it revs up again.

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Have you checked your Co Potentiometer (the air sensor in the pipework going from intercooler to throttle body). This poor idle sounds like the sensor could be giving a poor reading and would explain bad idle as ecu will be thinking more, or less, air is coming into the TB. Had this on mine. Did you say your fuel economy is bad too? this would also explain that.

Worth a check with a multimeter :)

Edit: Just re-read your symptoms. did your guy at the garage adjust the Co Pot when it was in there? You mentioned he adjusted something? Why did he do it? and what did he do? :)

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