Car is a 1998 A4 1.8T (5 speed manual).

Just noticed this today when I got to the store, put the e-brake on and was checking my phone with the car idling in neutral- the gas warning light went on and beeped. I thought it was weird because I was almost positive I was at half a tank. I turn the car off and right back on again and it's just above half a tank where I thought it should have been.

I drove the car a bit later and noticed how when I started driving I was still at around half a tank, but after driving a couple of miles it was down to like a quarter tank, and by the time I reached my destination it was almost at the point where the gas light would come on again. I sat in my driveway with the car idling for ~5 mins or so and watched the ticker slowly go down right before my eyes.... then when it had almost reached the "E" the ticker flies back up to around the half tank mark again where it should have been.



Now the thing is I'm not really worried about this and have no problems driving the car; it runs fine, nothing is leaking, no weird noises, etc. I just wanted to get some second thoughts from people with more knowledge in that this is not a serious issue that I should look into fixing immediately, or if its just a bad sensor of some sort.

 

Its the fuel sending unit. Common failure.

Best thing to do is buy a new fuel sending unit on ecstuning there about $50 bucks but u can sometimes find them from partouts. the s4 one is the exact same

1. Go to the gas station.
2. Fill up on 93 octane til the pump shuts off
3. Record how much gas it takes. A full tank should be about 15 gallons.
4. 15 gallons is probably around 320 or so miles give or tank.
5. When the gas is getting close to empty just change the fuel sending unit.

It took me and my buddy 20minutes and a little bit of clean up cause I still had a lot of gas. Theres a diy if you search "b5 a4 fuel sending unit diy"

At first the problem is intermittent but it will soon completely fail.

 

yea that' crap is stupid i been having same issue but its a really easy fix mine just acts dumb when car sits over night i wake up half my tank is gone but then comes up when driving i just ignore it ama fix mine tomorrow.

 

You might be able to fix it too, I had the same issue and all I had to do was re-solder the wire that goes between the floater arm and body of the sender.

 

I need to go ahead and change mine...
it's been acting retarded since last Spring....

 

Just pull it out and repair it. 99% of the time you can fix it by repairing the wire and cleaning the resistive element with electrical contact cleaner.

 

That lines up with what I've been reading.. something like this Tech Article Title ...?