UseTheS4ce

I'm pretty sure my problem is Fuel System related. It used to be (a few weeks ago) that whenever I'd get down to about 1/4 tank or less my car would run real sluggish (slow response, doesn't accelerate as quick, etc). Right after I'd fuel up (always 93) the car runs normal again. I just figured it was "dirty gas" and changed gas stations.

Starting recently, my car is running sluggish like that all the time (I pressure tested it and noted no boost leaks). The other day I let the car run down near E and when I went to start it the day after, it didn't turn over on the first crank, tried it again and it turned (never did that before). Also, I've gotten some erratic readings off the mileage meter on the trip computer (usually reads ~320mi after a fill up, the other day it read ~450mi after a fill up). And, on the same fill-up mentioned here, the gauge went from almost 1/2 tank to about 3/4 tank while I was driving, then stayed there and went down like normal.

I picked up a fuel filter and I'm going to attempt to change it out this weekend, I hope that's the root. But I'd be open to any other suggestions, diagnoses, or a good sock in the gut. Thanks Buckaroos.

RKA

How many miles are on the car right now?

Have you checked for codes by any chance?

The erratic fuel gauge could be a bad sender. I wouldn't worry about it right now. Just in case, reset your odo at each fill up. That way you can use the odo as a fallback if the gauge goes really awry.

lemieux@curbside

like changing tones , and being any louder or buzzing at all ?
change the filter first and see how it goes.
(a tip: always look to put gas from a newer and of good quality gas station ..the tanks are newer and have less crap on the bottom)

UseTheS4ce

...but I did check for codes, I'll check those when I get home and I'll post them. The car has 60k on it now. It just sucks that when I bought it used from a dealer (@52K) there were absolutely no service records whatsoever, so I have no idea what was and wasn't done and when. But thanks for the input.

UseTheS4ce

...I don't really know what noises to look for, I have recently heard a low pitched hum though. It was very faint and hard to pinpoint but it's definately new. I guess i'll go with the filter first then see what happens from there. Thanks for the help.

LEDfoot

In the A4 the tank is a little bit like an upside down horse shoe, there is a secondary pump that moves fuel over from the one arm to the arm where the main pump has it's intake. If that pump was inoperational it could explain why you would get problems when you were getting low on fuel. I guess you can sock me in the gut now.

Hogothorpe

I would change the spark plugs too

UberVier

I'm 99% sure it's the pump. It may not be dying, but at the very least the uptake hose/system in the tank is amiss somehow. I dunno what the in-tank pump looks like, but I bet there's a hose or column that pulls fuel up, and it has either come loose or cracked, corroded, what have you.

I just spent a good long time tracking this same exact problem down on my ex-E30. Good luck.