Help! Engine malfunction:reduced power. stuck in Chicago

[Sophisticated Redneck]

Originally Posted by wagonguy

I had a very similar problem recently. 2011 M, bought in California, on the drive home to Nevada, got the engine malfunction/reduced power alarm. Pulled over, shut it down and restarted and all seemed good. Over the next two weeks kept getting boost codes and torque reading codes. It would shut off the boost and it would drive like a slug. Ended up being an old battery. Put a new battery in and registered it, ran flawlessly since.

Doug

Thank you for bringing this up. I forgot about it. This can happen in rare instances where the battery is not quite completely dead (just enough to start the car) but has very little capacity left. BMW has designed the charging system to only kick on the alternator during braking or when the voltage falls to an extreme low level or if certain high-drain accessories are turned on like headlights and foglights.

Have you ever noticed when you slow down and brake during the day you can hear your ac/heater blower fan increase in speed? This is why. The alternator turns on when coasting or braking. Now if you have a bad battery and decide to gun the throttle, it can drop so fast in voltage your computer goes nuts before the alternator kicks in and the voltage is so low the coils can't effectively fire, especially if they have some age on them.

So Always drive with your headlights and foglights on if your going to be stepping on it or if you think you have a weak coil or two. This causes the alternator to immediately come on and will keep the voltage at 13.5+ volts, otherwise it can drop as low as 11.3 before it forces the alternator to come back on. Grab a cheapy cigarette lighter voltage meter if you would like to see this insane charging system in action. It's how I learned that headlights + foglights forces the alternator on and voltage jumps nearly 30 percent in some instances.

Whoever designed the charging system was an absolute imbecile. All this for less then 1 percent gas savings.

TLDR version: drive with your headlights and foglights on if your racing or your battery is going south or as the first step to see if it has an effect on misfire codes.

[Haneifk]

ok, so i know in saying this i'll probably annoy someone or maybe even get kicked off the forum for overlooking something so simple? lol.

it was.......the air filters?

took it to the dealer this morning. they were able to reproduce the issue that i was talking about. started diagnostics, at one point diagnostics required air filters be changed... changed the air filters and the problem went away. I guess i assumed that no one would ever let an air filter go so long that it would get to the point that it would cause an engine to go into limp mode?

i still can't believe that's all it was.... really?!!?!?! is that even possible?

[Bennettrindge]

Don't freak this happens. When I bought my 2012 had lots of issues that were easily resolved with a good inde BMW mechanic. Get it fixed and go back to the dealership with a letter form the Attorney general. They will work with you!

[Bennettrindge]

Let me rectify. I bought my 2012 in mass and I live in NH. Most employees of dealerships are actually clueless! My 2012 had all sorts of faults and bald tires!! I bought it gladly. I spent $2500 fixing it up (mostly cosmetic) and went back to the stealership with all the paperwork and a letter from the attorney general from mass stating this and that. They said to me "you've done your homework haven't you." I said yea. They requested, "can you meet us half way" I said sure! They paid for my new tires and repairs and some cosmetics! I did put on 285's square which was a mistake but whatever. Stealserships count on ignorance of the consumer. They are just as ignorant!!! Know your rights and assert yourself!