Hello,

             i  have noticed something different when I start up my Mark 3 Fabia combi 110  for the first start of the day.  It starts up fine and  I reverse off my drive onto the road. No issues with any of that but when I engage first gear and drive forwards the engine note changes as though I have revved it hard when the engine is still cold but I  have never done that.  It is hard to describe but it sounds more "sporty". It  doesnt do it in reverse, only in first when  I  pull away.  If  I park up somewhere       and come back to it later it doesnt happen. Thats the case if I come back to the car  in a few minutes or in several hours.  Its only the first start of the day and only in first gear, not reverse.   i obviously notice it more if i have got my car window open as in this warm spell but  I can still hear it  easily with my window closed.  It doesnt happen when  I work my way up through the gears.  I can drive the car for hours in all sorts of conditions and it behaves perfectly and it never happens again, everything is normal.

 

               i am wondering if it could be an issue with the manifolds or if the exhaust is leaking somewhere.  I  know that the ecu automatically richens the mixture for the first start of the day but then I would have thought whatever is happening  would have happened in reverse for that first start but is doesnt.   I am off to  Northumbria in a few weeks  for a weeks break  and dont want any problems while  I m there. Surely, if it is the exhaust leaking somewhere I would hear it all the time on the road?  That applies,  I think, to the manifolds too? Unless, there is a gap between the manifolds and the pipes when its cold and the gap disappears when the car gets warm?  I am not seeing any increase in fuel consumption or  any loss of  performance.  I am not that great at fixing cars and will probably take it to my highly trusted independent but  I  really dislike mysteries.

 

                      Thanks for reading

 

                       

It has a Catalytic converter and that needs warmed and happens automatically even on hot mornings.  (It is not like a choke.)

When you reverse the flaps close in vents so you do not get fumes so maybe you hear the engine differently.

 

You do not say what age your car is but i think it is pre GPF (Gasoline Particulate Filter.) again that gets heated quickly to reduce emissions.

 

If the exhaust is suspect then get the car on a ramp but i think likely not necessary. 

I think that this has been discussed in the past on this forum, in particular this 1.2TSI 110PS engine, and maybe also the 90PS version as well. 

To be honest I've forgotten the exact mechanics of it or why it behaves like this, but I'm sure it has something to do with how the excess capacity of the turbo is diverted under these initial conditions.

My wife has a 2015 VW Polo 1.2TSI 110PS and I've hear that but mainly only after she has reversed back up our driveway and is then driving away on a level section of road, I can't say that I remember hearing it doing that when cold while I'm driving it - though it could be I'm expecting it and accept it as being normal.

 George,

             You are correct, its a 17 plate,  first registered 30th  June 2017. I  didnt know about the flaps in the catalytic converter or that they close when reversing.   i am going to monitor it and will very likely get my independent  to check out the exhaust quite soon.  I honestly would have thought that, if there is a leak or leaks  I would hear it all the time when driving?  Thats certainly what happened with other cars I  have had that had exhaust  leaks.

 

              Thanks for responding.

 

Not Cat flaps.

The flaps are in the heating / fresh air system.

Closed when in reverse so you do not get fumes and in your case a different noise.      Listen to the car from outside with someone driving forward then reversing.

Most people start the car up and drive off immediately, even I sometimes do it in the modern car (Fabia) but I still think it's worthwhile to do the old fashioned thing as with cars from the last century, that is turn the ignition on (all entertainment and communication off (not turn back on) and give it a second or two whilst you check all the warning lights and gauges, and put your seatbelt on.  If everything checks out start the car, and give it 10, 20, 30 seconds before pulling off to hear the sounds of the engine and check the warning lights and gauges again to make sure all is well.

 

This won't alter all the stuff the modern car has to do to prepare and check itself and all the computers' programs to untangle their panties but it gives you a chance to get used to the different sounds at different times of year and environment.  I often think the Fabia sounds a bit different (or 'rough') from initial start up and left a number of seconds, but if it's the same different (or 'rough') under the same circumstances as the previous time(s) and everything runs well I don't worry.

 

When you hearing sounds you've not noticed before you then start to listen harder and can hear other sounds too, sometimes they do need investigating other times it's just a matter of the sounds have always been there but you've not noticed.

 

ETA: I had no idea about these flaps either, I'm surprised the windows are allowed to be down.  On my car, when cold, I start it with the choke, fiddle with the choke cable to get the right amount of fast idle, then reverse out through the petrol enriched fumes, often thinking I could have done with less choke.  

 

Edited 21 July, 20214 yr by nta16

Just the one flap, the one that changes position to block external air supply to the cabin fan when you select 'recirculation'.

Top of shot here, in non-recirc position,  cabin fan visible behind it. It turns through about 90 degrees on its left/right oriented axis to block that big rectangular hole when in recirc position, which reverse gear causes to happen automatically.

This is on a mk1 but I'd be surprised if a mk3 was wildly different.

 

 

 

Mk1's.

http://briskoda.net/forums/topic/363392-heater-blows-faster-in-reverse

I have never driven one, only mk2's & mk3's & DSG's and i knew something happened when reversing but then i am Mutt & Jeff.