Bubbles in fuel line normal or not ?

[Flufy]

HI I have the 3lt TDI engine in my A6 and when i am accelerating hard the enigne goes into limp home mode, i removed the TDI tuning module just in case that was causing the problem and then i spotted bubbles in the fuel line (see link to video) Audi A6 3lt TDI Engine fuel line bubbles - YouTube .
Are these bubbles normal or is their something wrong ?

[Doctle Odd]

It could be sucking a little air at the fuel filter, is it genuine or a cheapo filter. I think a little air in the fuel would be ok but i'm open to correction, I'd check all fuel lines and connections first and replace the filter. I think timing being off off can cause this as well

[Guest 2]

Limp mode = fault recorded

Get a fault code scan done

[Flufy]

Limp mode = fault recorded

Get a fault code scan done

Will do its going in tomorrow, thanks for the replies

[rafletcher]

As air is much more compessible that diesel, I would expect bubbles in the fuel to give fuelling problems - and no, it's not normal. I don't know the structure of the fuel delvery system, but I assume there is a pump in the tank 9low pressure) and another on the engine (high pressure). As the whole system is pressurised I'm not sure how it would be poissible for air to enter at the filter - as opposed to fuel leaking out. Unless perhaps the fuel filter is badly clogged, and the HP pump is "sucking" fuel through it, and introducing air that way.

I would suggest changing the fuel filter and getting the fuel lines bled of air (small bubbles are amazingly tenacious and persistent!) if the fault code doesn't show anything mecahnical/electrical as the cause.

[Flufy]

Well car was at an Audi dealer today and they changed the glow plugs ( shown faulty from previous scan ) and fuel filter, as soon as my wife arrived home i took a video of the fuel line again with the engine running - Audi A6 no bubbles in fuel - YouTube .
No bubbles so i took the car out for a spirited drive and no limp home mode
I know it is early days but i could get the limp home mode to appear at will before the fuel filter was changed.
But there is allways a but, the car has both inlet manifold bank problems and £1300 quote to replace both we will have to see what the waranty company say's

[rafletcher]

Ok, the swirl flap linkage issue (which if you have it should result in the engine management light coming on and staying on) will NOT cause limp home mode, or indeed any other symptom that you would notice, other than the light. And there are other cheaper fixes than £1300 to an Audi dealer, especially if no Audi warranty cover. Your third party warranty may well not cover it (I've read elsewhere that it's so common and expensive that Warraty Direct won't pay). So if you find that 1) get a quote from a non-franchises audi specialist whose labour rate will be half what Audi charge. 2) if you're within reach of Iver in Buckinghamshire (or even if you're not - it may still be much more cost effective to pay a visit) look up Fontaines - they have a fix (which I believe is a replacement linkage, as it's linkage ball joint wear that causes fractional positional errors in the flaps and gives the error light) for around £250 per side - so £800 less than your quote from Audi. or 3) if you or a friend is a handy mechanic do-it-yourself with replacement strengthened manifolds from eBay for around £400 all in - see sticky at the top of the forum.