Buzzing Noise, Intremittent. Stalls Whilst Idling

[Schuey]

Ford Focus 'W' plate. Zetec 2.o 16v Petrol.

With engine running, regular intermittent buzzing noise, you would think it was the cooling fan, but it isn't. If allowed to idle the car stalls, if it buzzes whilst in traffic and I add just a few revs it goes soon after and doesn't cause the car to stall.

Any help would be appreciated.

I would like to mention that the car does not have two silencers, it just has the rear one, the centre one has a straight through pipe added at a later date, I mention this in the event that it could make a difference.

Thanks

[jeebowhite]

Buzzing noise to me jumps out potentially as alternator? do you get the battery light just before it stalls?

[Schuey]

Buzzing noise to me jumps out potentially as alternator? do you get the battery light just before it stalls?

Hi, no there is no illumination on the dash for the alternator, the noise doesn't seem to be coming from that location.

Thanks for you reply.

[jeebowhite]

The thing is the buzz should be something mechanical, maybe a pump if not the alternator. at the moment their is not much info to go on. Does this happen when you start the car and just leave it to idle, or do you have to be driving for a set period before hand?

Im not quite sure at the moment otherwise...

[Schuey]

The thing is the buzz should be something mechanical, maybe a pump if not the alternator. at the moment their is not much info to go on. Does this happen when you start the car and just leave it to idle, or do you have to be driving for a set period before hand?

Im not quite sure at the moment otherwise...

Usually within 1 minute of starting the car, however it can buzz whilst I have been driving for a few minutes, one of those intermittent faults. I have heard that IMRC Inlet manifold runner control units fail, however I do not have one located in either of the front wheelarches, that is not to say I do not have one. The buzzing lasts approx 20 seconds then it stops, I was wondering whether it could be a valve, could it be the Idle control Valve, this may cause the car to stall if it were malfunctioning perhaps?

Thanks for your replies so far and anyone else whom can shed some light on an annoying and intermittent fault, I am sure other people have experienced this, I cannot be the only one.

[jeebowhite]

Could be idle control, it makes sense that if it struggles to maintain then it stalls, but I just dont understand where the Buzz sound itself is coming from. The sound in my head is like standing next to a small power substation? or when you turn the electrics on with an old diesel where it buzzed for a few seconds, and the glow plugs light up. May be worth checking the EGR valve if you have one also, not got too much knowledge on inlet manifolds so cant really comment on that.