Audi Quattro Faulty fuel sending units - car junky
I read very recently that Audi America recalled some 50,000 A6 Quattro models (1998-2000)for faulty fuel sending units.

Sulphur deposits on the fuel sending units (3) gave false readings such that empty fuel tanks gave the impression that there was fuel in the car. This was common to quattro models due to the way the fuel tank is mounted.

My Audi A6 2.8 quattro 1999 auto has a somewhat of a jumpy fuel guage, such that one moment it will read e.g 1/2 tank, will go to just above 1/4 and then rise once the engine has warmed up. I know that the car is quite thirsty (24 mpg avg)but sometimes the movement from one drive to another is too much!

I would like to know if this a common problem among other quattro owners and if there are any fuel additive products that may remove such Sulphur deposit build up on the sending units?

Is this common only to A6 or do A4,A3,A8 quattro owners experience a similar thing?
Audi Quattro Faulty fuel sending units - Wally Zebon
I had a problem in my S2 (admittedly a bit older) where when the fuel guage got below ½ a tank it was very erratic. One minute it would read ½ full and the next empty. The range function on the OBC played up as well

It turned out to be a broken wire on the sender unit in the tank. When full the two ends of the wire made contact, but once below ½ full the contact broke giving a reading of empty.

Might be worth investigating. A new sender unit doesn't cost much and its a 1 hour job to fit it yourself.
 

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