Maybe wishful thinking but my car "woke up" after having the battery disconnected for some time. It used to be sluggish and it now feels it has a more power, has anyone else experience this behavior? My car (2008 528i) was at the body shop for about a week, the passenger door was replaced, the shop disconnected the battery because of the electronics on the door, when I picked up the car, idrive had a message about "battery discharge" the shop connected their hand held diagnostic tool through the obd2 port and reset the message. No battery problems so far, but the car feels like it has more power. Do these cars learn how you drive (or previous owner) and set themselves for that style of driving, but when the battery is disconnected, they reset themselves?

 

The car learns your driving style and adapts to it. Your transmission was reset when the battery was disconnected. If you sprint drive it will stay like that if you start to drive like grandma it will respond as so.

 

I drive fast but accelerate slow. I thought that you can reprogram the transmission by pressing the pedal to the floor with the key out or some combination like that. Not really a issue for me since I just use sport mode when I want more pep.

 

My MPG was stuck at 20.9 and after the reset and about one week it went up to 21.3 - more power and better gas mileage after the reset.

 

Hmm, you might have something there.
About a month ago I replaced the battery. I did not keep power to the car during the switch over. I only had to reset the time since all other settings remained intact.
Within days of installing the new battery we went on a 10 day vacation and drove a total of about 1,300 miles. Mostly easy highway miles.
During the past week I did some preventive maintenance, like coolant replacement and oil change and was especially attentive to how the car behaved to make sure I did not mess up anything. More than once during that time I noticed how much smoother the tranny shifted, both in normal and sport mode. Today I did a little warmup run to get the rear diff. ready for a fluid change, and I noticed it again. Then I read this post. Very interesting ...
About the pressing down on the accelerator: After extensively servicing the AT and especially after wear parts have been replaced along with a fluid change, this procedure resets parameters which compensate for the AT's wear.

 

Yeah, that's the same feeling I got.

The tranny fluid was replaced about two months ago, tried the reset with the gas pedal procedure but it never did anything for me. The battery reset change was definitely noticeable.

There's a street near my house I commute often, it's an uphill, my car would feel heavy going up the hill, it doesn't struggle as much anymore, fairly smooth ride up the hill. This is probably where I noticed it more.

 

I think it might be related to the new Teflon paint theses shops are using. It cuts down on the drag coefficient and really makes the car behave much better. JK, I too think its related to the trans reset.

 

hahahahaha. I think it's the placebo effect. Or could be that the capacitors of the elctronics drained clearing learned adaptions...but I don't think this is the case. I think it's placebo after driving another car. If it were true that disconnecting the battery drained the electrical system the same effect could be done if you take both terminals off and touch + and - together for a good minute, draining the electrical system resetting everything.

 

Not a placebo - I agree with the others, it must be related to the trans reset.

 

I dropped off my car this morning at my trusted indy for unrelated repair work and I took the opportunity to bring up the tranny reset thru disconnected battery. He knew about it and explained it with a glitch in the AT programming and that sometimes the result can be experienced thru improved shifting. It seems to be random and is not repeatable.