So, I found 2 swithblade keys and the valet key in the spare tire compartment in my 2001 A6 which I purchased from a small dealer last summer.

I previously just had one aftermarket key with no remote. The "found" keys have a bit of surface rust. They fit into the car, and will start it but when they do the flashing light on the dash comes on and the cars bogs down, then dies. They work in the doors no problem. I replaced the batteries in one of the switchblades and tried to program it with the "original" key in the ignition and the "found" key in the door, but it doesn't beep or work or anything when attempting the process which I read about. Any suggestions on where to go from here? Thanks.

P.S. I have searched the forums and tried the steps I have found.

 

I believe you have to press UNLOCK on the remote, open the door, insert the key in the ignition, turn to 'ON' and then press and hold UNLOCK on the remote until you hear a click from the car. That should let the car see the remote as a viable ignition and door key.

 

There are two things relating to the keys. One is the remote sync which allows the key to unlock and lock the doors. The other is the immobilizer setting. Sounds like your immobilizer settings were changed. Unfortunately it is dealer only procedure. If you have VAGcom you can access the funtion, but you still need PIN generated by the dealer only.