I replaced the alternator in my 1999 Audi A6, now the car doesn't want to stay started. It will turn over and start, but it shuts straight off. If I keep my foot on the gas it will stay running but it lurches. No wires are unhooked. I tried to drive it but it wont even get up to speed it wont go past 2500 rpms. Please advise on what i should do.

SOURCE: Audi Quattro A6 will not go into drive

It's the brake pedal switch. There is a switch down on the pedal arm that closes when you press the pedal down, and sends a sensing voltage to the controller, telling it the brakes are applied. This allows the transmission lock to disengage so you can shift out of Park. When that switch fails, the lock won't disengage. You need to replace that switch and you'll be fixed.

SOURCE: my rear tire on my

Has the tyre been trmoved recently ?
It could just be that it has been refitted not using the Audi spike supplied to ensure that the rear disc and wheel are properly centered. Try loosening the bolts ands wriggling it to see if it reseats both propery.

SOURCE: lurching start 2004 Audi A6

try the coolant temp sensor...if its getting the wrong readings then it will fuel accordingly....

SOURCE: Battery light stays on until I press the gas

Known issue to occur occasionally on VW/Audi. What is occurring is that the alternator is not spinning out fast enough to start charging, so the light is on. Once you rev the engine, the alternator starts to charge and remains charging till its shut off and restarted. It can be related to too low of an idle (not adjustable, unless you have a dirty throttle plate or air leak), the alternator itself (aftermarket or a bad rebuild) or an incorrect alternator pulley installed (too large).

SOURCE: I have a 1999 Audi A6 quattro, have just changed original fuel

You have to bleed the system, most likely air, or you blew the fuel pump fuse !