Throttle needs broadband?

[wipash]

Hey,

The throttle in the 2000 Legnum GDi I bought about 3 months ago has (I think) a problem.

It sounds like an old dialup modem.

That's the best description of the sound i can come up with. It's only audible when the ignition is on but the engine is stopped. It changes pitch and tone depending on accelerator position, and goes a bit mental for 10 seconds or so after I turn the ignition off fully.

Is this a sign that it's about to die? Seeing as the throttle is quite integral to me going places in my car, I'd like to get it fixed/replaced before it dies.

Has anyone had any experience with this noise? I asked my mechanic, and he said he'd never heard it before.

Thanks,
Sean

[Turbo_Steve]

Er....I am only guessing here, but this sounds like it's maybe your idle control motor? That' lives right underneath the throttle butterfly, so if that's where the noise is coming from, it's liable to be that.

As it only happens when the ignition is on, it's almost definitely going to be something electrical.

Is it definitely coming from the throttle plate of the engine? Knowing EXACTLY where the sound is coming from will make a lot of difference.

[wipash]

I don't know too much about the inner workings of the throttle, but I did some investigating.

The noise continues for 10 seconds or so after the key is turned off, so i got a friend to push the accelerator and turn off the key. Watching through the air intake, I unplugged the cable going to the throttle. The noise stopped instantly and the throttle snapped closed (usual operation, I assume). I plugged it back in straight away and the throttle opened and the noise started and continued for 2 or 3 seconds, after which the throttle closed again and was no longer responsive to accelerator movements.

[Davezj]

is it an auto and do you have cruise control?

or are you just diconnecting the Throttle position sensor (TPS) on the throttle body, the bit with the butterfly valve in it where the air goes in.

[Turbo_Steve]

I think Dave is onto something with the cruise control idea, there. Also, is the GDI a throttle cable, or a pneumatic actuator?

[wipash]

Auto, no cruise control. Noise is coming from the bit in the red box, stops when i unplug the plug in the blue box. I believe this is the servo that controls the throttle?

Throttle Body


Edit: Haha, I sound so untechnical. Sorry guys

[Turbo_Steve]

That's your idle control system. To be honest, it may be an early sign of failure, which will lead to stalling. But it may simply be noisy.

If you're worried, I'd take off the throttle body, remove the idle control, give the whole lot a damn good clean, reassemble, and not worry about it.

Chances are it's going to seize at some point, so start trawling the wreckers yards for one nice and cheap.

[wipash]

Cool, I'll give that a go in the weekend. Thanks so much!

[elnevio]

Good luck!


And you win this week's prize for the Best Aural Description Of A Problem Noise!

[Turbo_Steve]

Awh Nuts!!! Pipped to it again!

[psbarham]

if its a 2.4 then they are fly by wire, so that's probably the source of the noise

[bradc]

2.4's do not have a physical throttle cable, which could mean more complicated problems than just the idle control.

[Turbo_Steve]

AH!!!!! So the noise will be the motor farping around with the throttle butterfly.

[crazydriver81]

take it easy guys...that's just normal for GDI engines. My Carisma GDI did the same and I went to the garage.
This is the high pressure fuel pump which is connected to the injectors and the accelerator pedal. I'd say you should have concerns if it doesn't make this noise.

[wipash]

Thanks for the ideas. I think I might take a video and put it up so you can hear it exactly.

Used a stethoscope to confirm beyond any doubt that the noise was coming from the bit circled in my earlier picture.