Is there a definitive answer to the Crazy Fuel Readings problem?

[JMGR33N]

OK, so I've had my Avant a week now and I'm loving it!

The one thing I've found pretty disturbing is that the fuel gauge seems t have a mind of its own. I left home with 1/4 tank showing on the gauge and 100 MTE.

I sat in traffic because of an accident and the gauge stayed put and my MTE went up to 145, which is fair enough and what i'd expect.

I then pulled off the motorway leaving the crawling traffic, drove for 1/2 a mile and just as i pulled into my work carpark, the fuel warning light popped up. the fule gauge suddenly then read empty and 5MTE!!!

Now I've read a hell of a lot of posts about this on various forums, but i'm still yet to come across a definitive answer as to what causes it. which is odd as it seems so common.

Does anyone know if there is a confirmed root cause for this issue? seems a very "un-Audi-like" problem...

Thanks.

 

[Molnboman]

OK, so I've had my Avant a week now and I'm loving it!

The one thing I've found pretty disturbing is that the fuel gauge seems t have a mind of its own. I left home with 1/4 tank showing on the gauge and 100 MTE.

I sat in traffic because of an accident and the gauge stayed put and my MTE went up to 145, which is fair enough and what i'd expect.

I then pulled off the motorway leaving the crawling traffic, drove for 1/2 a mile and just as i pulled into my work carpark, the fuel warning light popped up. the fule gauge suddenly then read empty and 5MTE!!!

Now I've read a hell of a lot of posts about this on various forums, but i'm still yet to come across a definitive answer as to what causes it. which is odd as it seems so common.

Does anyone know if there is a confirmed root cause for this issue? seems a very "un-Audi-like" problem...

Thanks.

Hello JMGR33N

Not sure of an exact scientific explanation for such varying mpg readings. I always thought the ECU averaged the engine consumption versus what it thinks is left in your engine and then gave you an average. Am sure someone more learned than me will give you the correct answer.Secondly, I wouldn´t recommend that you measure your fuel consumption using the display. Not sure if you have a petrol or a diesel, however, petrols do not like idling in traffic. The fuel consumption at idle can be a bit scary, these B7´s don´t like standing still! I recommend you sign up to Fuelly.com and measure your mpg by recording your fill ups v miles there. www.fuelly.com.

Good Luck,
A

 

[desertstorm]

Why would you expect the MTE to increase when you are sitting in traffic and not moving ?? .
The car is using fuel and you are going no where so I would expect it to go down. I have found the MTE to be fairly useless, when you fill the car it reads way over what I know the car will do and pretty much stops that way till the last 50 miles when it seems to count down really quickly.
It's all about not letting you run out of fuel I think, when the car says 0 MTE there will actually still be several litres in the tank.
The trip computer readings are just for information, they are not always accurate.

Karl.

 

[JMGR33N]

The reason I'd expect MTE to temporarily increase when you first sit in traffic is because the car has been working out as you go along at normal road speeds the calculations for MTE.

If you then suddenly come to a standstill it takes time for the car to adjust the calculations to account for the lack of throttle movement and the MTE goes up temporarily.

If if you then drive on or leave it long enough for the calculations to catch up the MTE figured will level out again.

What I'm trying to find out is regardless of what the MTE says. The gauge seemed to suddenly drop from 1/4 tank to zero for no reason. I've seen lots of talk about faulty senders etc. but no confirmation of what causes the gauge to behave like this.

 

[Jespy]

i just hit the trip every time the warning light comes on - then use my experience of the car (1.9tdi = 50 safe motorway miles or 25 safe town miles) to work out how long till i should fill up. fortunately the audi fuel light works off a level transmitter which is better than the system that i had in my old ford that used to work of the MTE reading (as soon as you hit 50mte the light comes on)

i dont trust the mte one bit! i use it purely as a guide, and go on my past knowledge of fill ups - and how many miles are on the trip to work out how long i have left to fill up. i normally average 85 miles per £10 and only ever put in factors of £10...so quite easy to go off that basis

 

[JMGR33N]

Thanks jepsy that useful.

I had a Mk3 Scirocco last and i used to ignore the fuel gauge and soley go off the MTE. I guess i just need to get used to it. it was the jump in readings on the fuel gauge that kind of threw me though.

 

[Jespy]

Thanks jepsy that useful.

I had a Mk3 Scirocco last and i used to ignore the fuel gauge and soley go off the MTE. I guess i just need to get used to it. it was the jump in readings on the fuel gauge that kind of threw me though.

yeah pal on a 10 mile journey my mte can swing by up to 100 miles which is CRAZY haha. fuel gauge is the best bet

 

[JMGR33N]

Hey all

Bit more info now that I've had time to get used to the car.

The readings are still a little funky. On the way to work today I came off the motorway and stopped at the traffic lights at the end of the slip road. At this point I had 1/4 tank showing on the fuel gauge and 145miles showing on MTE.
While sat there the fuel light suddenly came on, MTE showed 10 miles and the fuel gauge dropped from 1/4 to Empty.

Surely that's not right?

 

[Mike_B]

Sender unit faulty?

 

[Jespy]

Hey all

Bit more info now that I've had time to get used to the car.

The readings are still a little funky. On the way to work today I came off the motorway and stopped at the traffic lights at the end of the slip road. At this point I had 1/4 tank showing on the fuel gauge and 145miles showing on MTE.
While sat there the fuel light suddenly came on, MTE showed 10 miles and the fuel gauge dropped from 1/4 to Empty.

Surely that's not right?

Yeah dude. 100% not right!

 

[JMGR33N]

Sender unit was my first thought, but theirs a fairly recent receipt I got with the paperwork for the car that said it'd been replaced.
Guess I can't really trust that completely.
Anyone know how easy replacing the sender unit is?

 

[JMGR33N]

Just seen on a DIY guide that the quattro has two fuel senders. One on the left of the tank and one on the right. I guess one of them could be faulty.

They are easy enough to take out an look at so I might do that when its a little less frosty.

 

[JMGR33N]

I guess this is as good a sign as any as to what the cause is. dug out my VCDS stuff...

1 Fault Found:

00438 - Fuel Supply Sensor 2 (G169)
010 - Open or Short to Plus - Intermittent

 

[JMGR33N]

Just a little update. I've not changed anything. But after reading out my error codes and clearing them, my fuel gauge had been behaving itself perfectly.

Like the error ouput says: Intermittant.