Replaced battery, engine control goes nuts

[SRR2]

Hello all. Longtime BMW owner but newcomer to these forums.

Unfortunately, my first post seems to be about a problem. I'm hoping someone here has dealt with this before and can push me in the right direction. Basically it's this: I needed a new battery. Removed the old one, drove to Sears, returned and installed the new one. Total power-down time perhaps two hours. Now that we're up and running again, it seems that the Motronic has lost its mind. The engine idles at 1500-2000RPM sometimes, the fuel cut-off doesn't work at all, and when shifting the engine 'hangs' at the peak RPM attained so that letting out the clutch in the higher gear is a jerky proposition. Without the fuel cut-off, there's no engine braking either. And, to top it all off, it's burning gas like an M1A1.

AAARGH.

Aside from having to connect the battery charger if the car hadn't been run in a few days, the pre-battery change state of affairs was perfectly normal. Car ran perfectly and averaged 26 or so MPG. I haven't measured the mileage since this fiasco, but it looks sub-20.

This morning I ran the car around to warm it up and disconnected the battery again for about 20 minutes. Reconnected it, drove off, and discovered that the problem is worse, if anything.

I need some serious advice here. Thanks for reading this post.

[632 Regal]

do a stomp test.

[MSM]

Maybe you disturbed some other wiring when changing the battery. Maybe a dodgy fusible link could lead to these symptoms?

[Phil Sanderson]

...get back to normal running after disconnecting the battery. Your revs are high at idle - my 525i revs are always low after reconnecting the battery, car wants to stall all the time, I just turn on the air-cond to bump up the revs a bit.

Just play along with it for a few days until the computer "learns" what it is supposed to do.

regards
Phil

[SRR2]

...get back to normal running after disconnecting the battery. Your revs are high at idle - my 525i revs are always low after reconnecting the battery, car wants to stall all the time, I just turn on the air-cond to bump up the revs a bit.

Just play along with it for a few days until the computer "learns" what it is supposed to do.

regards
Phil

The 'brain' in this motronic (moronic?) seems to be a slow learner. (What the heck is a 'stomp test'?) Funny thing was that after my last attempt at resetting it, it started up and idled right at 700, smooth as proverbial silk. The fuel cutoff worked as advertised at 1500 or above. Business as usual, and I was a happy camper. Emphasis on "was". After about 5 minutes of driving the weird crap reappeared. Fuel never cuts off. Idles at 1800. And I use the term 'idles' loosely. It's driving me nuts, and the car is borderline unmanageable under these conditions. I will take your advice and give it some time to settle in. Thanks.