Audi Repair: Idle speed too low, throttle position sensor, audi a4 quattro

Question
Hi- just replaced battery (which was a tight fit) in my audi a4 quattro 2.8 1997. Now when i drive the car it keeps stalling- when i slow down the idle speed goes below 500 and cuts out-- not good as it takes out power steering so have to restart engine as i turn into roads etc-  any help greatly appreciated- i presume i need to increase idle speed but do not know where the control valve is ? Thanks

Answer
The ECU sometimes recalibrates when the battery power has been disconnected, but normally this sorts itself out in an hour or so after starting up.  It sounds like your problem may be the idle control valve electically driven and not adjustable) or the throttle position sensor (needs to send a signal that the throttle is shut to activate the correct idle circuit) or the Mass Airflow Sensor (responsible for the correct mixture at all running conditions)  I would get a readout of the fault codes (if any) to get an idea of problems indicated in the ECU.  Let me know what you find,  Jan