1.2 TSI Fabia Mk2 estate, 11 plate.

 

Hi all,

 

I've got this strange low sounding knocking noise issue that only occurs when

a) i'm idling (ie clutch depressed  or in neutral) and

b) when car is not moving, ie mainly when at traffic lights etc and i've stopped/got handbrake on.

 

The engine is idling around 650 revs at this point.

 

I can make the rattle/knocking go away by

a) feathering the accelerator and making more revs

b) keeping my foot pressed on the clutch , taking the handbrake off and rolling.  The wheels start to move at this point which makes the revs rise to around 800 and the noise goes away.  The revs rise without me pressing the accelerator.

 

So, is 650 revs the correct idling rate for a mk2?  If not, what should it be and what could be causing it to be lower than expected?

If 650 is correct, where is the noise coming from?  The bloke on the service desk suggested its in the cabin/dash, but i'm not so sure.

 

I've just had the car back from the main dealer where they have replaced the timing chain under warranty.  Although this sound issue was there before this work was undertaken, so i'm not sure its related to that now.

 

Any thoughts would be very much appreciated.

Have been doing some digging/searching.

 

It would appear the rising of the revs when starting to move is normal, its an anti-stall method..... so can rule out that red herring.

 

Found this comment on a post that suggests the low revs noise may be coming from a fuel pipeline moving around.  He includes a photo too, which is helpful.

The OP says 'passenger side noise', but he's from the Czech Rep so his passenger is my drivers side, which is the general direction of where it emanates from.

 

 

So i'm going to put my head under the bonnet and see if the noise comes from there.

If it does, i'm not exactly sure what sort of material to stuff in there to deaden it?  

He talks of 'absorbing sealing' and 'black plastic sealing'?

 

Obviously, the other cure would be increase idle revs from 650 to 800, but not sure how to do that, i'm assuming the ECU plays a part in that and garage intervention required? (i'm no mechanic!)

 

Cheers.

Edited 19 November, 20187 yr by Zarch

More 'rattle' threads that point to similar to above.

 

 

 

Just need to wait until the weekend so that there is some light in the day for me to take a look...... :(

I have a kind of rattle when idling too. If I dip the clutch, it stops and if I increase the revs, it stops, too. My idle speed is around 800 or so and I need to increase it to around 100 to stop the noise. I thought it either the clutch and/or release bearing or perhaps camshaft and/or injectors. Seems to have no adverse affect on the running of the vehicle, though.

Some progress.  The knocking at 650 revs when idling is definitely in the area as per the referenced threads above and as highlighted in the first photo.  In front of the drivers side (UK) at the top of the engine.

 

That bracket has some play in it.  If you push the pipe fitting down towards the floor and hold it there, the bracket moves down and there is no noise.

Pull the pipe up and let go, the bracket moves and a rattle occurs when idling at 650 revs.

 

So my hooky fix for now is to dampen the sound as best I can with some pipe insulation.

Whilst this works, I fear only for a short while until the pipe and bracket work their way upwards again.

 

On the outer side of the bracket there are notches where it attaches to the body to hold it in place.  I'm wondering if something like some Sugru might set and hold it firm?  Suppose this depends whether is 'both' the bracket and pipe or just one of them that is the cause?

 

If anyone has any thoughts on this or suggestions it would be appreciated.

 

On a positive note, at least this is only a rattle and seemingly nothing too serious.