well Im' new to this site, I'm an Audi Freak have had over 15 different audi's, currently I have an a8, and a 2.7 6-speed A6!!!

Now my problem is I bought a 1999.5 Audi a4 2.8 quatrro Automatic for my girlfriend about 2 months ago, the car has been great until yesterday.

she called me yelling of course saying her car wouldn't start, so I left work brought a jump box and went to see what the problem was, Didn't start when I got there but still had power, so i jumped it. Started right up, than drove it around for awhile shut it down and still didnt' start..

So I checked the battery, it was bad.. So I replaced the battery on the car, and it started right up. So i was exicited about that, didn't drive the car right away because I had to get back into work. After work I went to get in it to bring it to her work, and it started right up I was pulling down the driveway and the car wouldn't go past 30mph, to make a long story short, I hooked up the computer to it, 6 codes came up!!
1545- Idle speed control
p1857- transmission control
p1426- emissions codes
p0102-mass air flow
p1129-fuel air
p1127-fuel air

Now I cleared all these codes, drove it around until the check engine light came on, and than checked to see what code came up first, 1545, came up first... Idle speed control..

Now this is where i'm lost, does anyone know anything about this or have had this happen before, I may be wrong, just need to get some input, I'v never had to change a Battery in any of my Audi's before, thanks for reading, and i'm open to any ideals to fix this problem!!

Vv

 

1545 = throttle valve malfunction possible problems are throttle valve tight/sticking, wiring, throttle control unit.

clean the throttle body out

edit: whats the battery go to do with anything? but if you need to remove it ensure you have radio code

 

Yeah, if cleaning all the carbon build up doesn't fix it perform a throttle body adaption.
Turn the key to the "on" position for about 10 minutes and the throttle unit should adapt itself.

 

Recharging/swapping a dead battery can have ill effects on Audi/VW cars. Especially DBW ones. I had a throtle body fault code after I jumped my dead battery once. I searched on it and found tons of people with the same/similar problems. I was unable to perform a tba/clear the fault code for a while until one day it just cleared and I was able to adapt it. So ya, clear codes and do a tba.