I'm trying to locate the cause of a whining noise coming from the front of the engine.

This noise appears when I turn the key to position III, but without the engine starting. If I then turn the ignition switch off again, the whining disappears with a 'clonk' noise. It's not always a constant whine - sometimes it sounds like its pulsing.

I'm fairly sure it's coming from a component positioned on the main air intake. If I first remove the lead (as per attached photo), and then turn the key, there's no noise.

I'm guessing that's some sort of air mass flow sensor ?

Otherwise, the engine (1.8 Duratec 125PS) runs very smoothly, apart from (I think) a worn pulley bearing on the auxiliary belt side.

Can you tell if it stops when the engine reaches normal operating temp?

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Hi GMo,

The noise is still there even if the engine is warm.

Any ideas what component that red lead plugs into ?

After a bit more research, it seems the red plug connects to a sensor on the throttle body. So I'm guessing it's something like a throttle position sensor ?

3 hours ago, SeaGrey said:

red plug connects to a sensor on the throttle body

 

The throttle actuator is probably energised by a pulse modulated waveform from the pcm (engine computer). This could be the noise you can hear. It is usually about 1kHz (a fairly high pitched whine, if audible)

If the car runs ok, I would assume the noise is ok. If the valve is sticking or malfunctioning, it will give a rough idle, poor performance, or not run at all.

Peter.

 

Normal

Thanks guys - I'll refrain from any tinkering in case I introduce any other issues ;)

This engine consistently idles OK at around 750rpm (after warming up) and doesn't hesitate at any rev, so seems to be happy.

The bit that still concerns me slightly is that it makes this noise when the engine isn't running. My very rudimentary understanding is that with ignition on (e.g. position III), and engine not running, the ECU will be powering sensors, and doing some monitoring, but not 'actuating' anything, especially on a cold engine.

48 minutes ago, SeaGrey said:

powering sensors, and doing some monitoring, but not 'actuating' anything

The throttle probably springs fully shut. It makes sense for it to move to the idle or cold start position before cranking starts, for quickest start-up. Maybe that is what it is doing.

23 hours ago, Tdci-Peter said:

The throttle probably springs fully shut. It makes sense for it to move to the idle or cold start position before cranking starts, for quickest start-up. Maybe that is what it is doing.

That makes good sense, and probably explains the 'click' noise when I turn the ignition off. 

I think I've figured this out. The electric connection is simply the power source for the entire throttle body - as it's a 'fly by wire' accelerator. So this is powered with the key ignition switch in position II and III, hence there is a noise as soon as it's powered up, before the engine comes on. I don't know whether the electrical whining noise is a problem, but as it all seems to work, I won't worry about it.

thanks for the help.

29 minutes ago, SeaGrey said:

I don't know whether the electrical whining noise is a problem

Probably not, see my July 11 Post above.

1 hour ago, Tdci-Peter said:

Probably not, see my July 11 Post above.

Thanks Peter - sorry, I meant to acknowledge your previous post, as it was reassuring 

Apart from hesitation when moving from standstill (which isn't serious, but I'm still investigating as I like all to be perfect), it's all running very smoothly, and idles well at 750rpm once warm. So I agree that the throttle is probably working OK.

I feel I could probably just leave it all alone now, as it's a very nice drive now that I've renewed a number of parts. I've got some more questions, but will start other topics here....cheers.

see my july 11 post above also. lol

Thanks Ian.

I think my original concern was that the whining was a sensor, as that's what I thought the electrical connection was for (I'd not realised it was an electronic throttle at the time).

I've also read earlier today that with the key in position II, the accelerator pedal will control the throttle, even if the engine isn't running. This can make it possible (with an accomplice in the driver's seat) to inspect or spray some throttle cleaner without having to dismantle anything. In the end, I did remove the throttle body to have a look, and it was a very easy job (only the electrical plug and air pipe to remove first on my particular engine).

cheers.