Found the source of my hunting idle when hot.

[archiboy24]

For quite some time now my car has had a hunting idle when the engine and ambient temperature is hot. In fact, if I didn't keep my foot on the gas it would often stall. Very annoying in rush hour traffic. Originally I thought my O2 sensor had bit the dust, but when I unplugged it the problem persisted. So last night I finally got around to pulling the codes and it threw one for the idle switch, which is integrated into the throttle potentiometer. I tested it with an ohm meter as per the Bentley and sure enough, there was no continuity between terminals 4 and 6. I then adjusted the switch as outlined and the hunting idle went away. Now, however, it idles at just over 1000 rpms and it's throwing a code for the idle stabilizer. I'll have to go in and make some fine adjustments to the throttle pot to get the idle where it needs to be. The strange thing is that I suspect there is a broken connection inside the TP causing the open condition when expanded by engine and air temperature. I just don't get how the adjustment (which involves simply rotating the TP slightly) makes the problem go away. The Bentley is quite vague about this. Can anyone explain the electronic logic of this?

[UrS4boy]

Ben: I don't know if you have seen this from the AudiWorld UrS FAQ (best viewed in Threaded Mode BTW) but it *might* help (or not):

http://forums.audiworld.com/showthread.php?p=18930483

The TPS is quite common across the Audi range so finding one at a wreckers could be easy.

[archiboy24]

Thanks Dave. There's something similar on the SJM website. It actually describes a repair procedure. If the problem persists, I may crack it open to see if I can fix it.

http://www.sjmautotechnik.com/trouble_shooting/20vthrot.html