Yes your father is correct adaptive learning for the ECU/EGS, as you have an E34 luckily the E32 is the same , this is for a right hand drive so the cable mentioned may or may not be on the same side for a LHD that for you to find out, so here you go......We've all heard of the Magic Reset, and it certainly 'cures' quite a few problems. The 'cure' is actually a general reset of the 'learned' values that the ECU uses for settings like timing and injector dwell.
So, how do you reset? First, make sure you know your radio code! There is no need to disconnect terminals from the battery, remove the seat or join wires together, that makes absolutely no difference. You simply remove the trim from under the RHS rear seat (unclips), remove the securing bolt which removes the plastic housing and you will find the negative battery lead where it connects to the chassis. (mostly on E32)
Remove the nut (don't lose the nut down the gap) and then pull the lead away from the stud, pull it out slightly and rest it on the carpeted face of the seat. There is absolutely no voltage retained in the wiring so there is no point joining wires across things or removing the positive terminal, I can assure you that it makes no difference.
The time required to reset the processor is quite short, 10 seconds or so will reset the values retained in the ECU. If you keep the reset short then you don't lose the Odometer reading. I usually leave it 1 minute just to be on the safe side.
What happens after a reset? For a start the car doesn't usually tick-over properly and may stall. It takes a while for the ECU to get the hang of idling and tick-over usually starts at around 100-150RPM lower than it should do, it takes a few miles of driving before it gets the tick-over correct. Don't be surprised if the power-steering gives a kick when you are reaching a junction, this is because the idle drops below the effective power-steering assist RPM.
Why does a magic reset work? At the very least it 'forgets' the bad habits the ECU has learned while you were driving the car like a Granny. After the reset give the car some welly! It might learn some good habits.
Hope this helps...
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Last edited by marti5; 12-05-2009 at 08:06 AM.