I did a dumb thing and left my key in the aux position and drained the battery on my 2007 Outback. A quick jumpstart got the engine going with no problem, but now I am down on horsepower, especially at low RPMs. All electrical systems seem to work fine, no check engine lights, etc.

 

Does the computer have to re-learn proper fuel mixtures and timing or something?

If the battery went completely dead, yes the ECU will have to relearn long term fuel trim, timing, etc.

If the battery went completely dead, yes the ECU will have to relearn long term fuel trim, timing, etc.

Yes, and some of the ECU parameter values can take several drive cycles before they reflect your car/driving.

 

In addition, if the battery was really down, the alternator will use not-insignificant HP for a while to recharge it.

With my futzy altenator, i can feel the load come on and off in the morning (yes i know i need to replace it). Itys a tremendous pull on the engine.

It may take about 1000 miles for the ecu to learn that you drive like a nut (or a nun).

 

nipper