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Discussion Starter #1
My car has about 150K miles on it and I've been battling a problem for almost 2 years. The car runs rough on a cold start and then runs better but is still a little "off"....the power has been the same. Because the car is so old I've replaced the mafs, all the O2 sensors, spark plugs, coils, vanos, fuel pump and relay....just about everything you can think of.

So recently they realized that I might not have the latest "base" BMW software beneath my Dinan software (I have the Dinan CAI/exhaust, MAFs/housings).

They do this and tell me the car is running like a dream....I'm thinking....yeah right!

I get the car back....and it is.

For a couple of days.

Then I get a mild misfire in one of the cylinders (8 I believe). I turn the car off and back on....SES light goes off and its not misfiring....but its back to running not so great.

The shops says they got the code for a bad DME...but only one time and they aren't sure thats' the problem.

I give the car back....they fix replace the fuel relay....again (was done within a year) and give it back to me.

Same problems all over again.

I'm about the bring the car back in....(haven't checked the codes myself). But we are kind of down to the DME and the alternator (which tests fine in the shop but is original) as the only things that haven't been replaced.

I'm thinking that if updated software makes the car run like a dream....then suddenly it goes back to running poorly...

Its gotta be some glitch in the DME/memory for the software right?

Has anyone else been through this nightmare? I guess a bad DME could throw all kinds of codes?

Any help would be greatly appreciated.

I'm close to telling the shop to replace the computer period...code or not.

Thanks!
 

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I highly doubt that the computer is the problem.
 

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I'm thinking that if updated software makes the car run like a dream....then suddenly it goes back to running poorly...
I would put money on your alternator. When they flashed your car they put it on a big charger to assure adequate power to the DME. After a couple days of running with a weak alternator the Battery runs down a bit. Because of the volts that the alt is keep down to it is often hard to diagnose.
I just went thru a weak alt and although the car always started, odd time a tad weak, I started getting weird codes that made no sense. I had the odd misfire on 6 and started getting CPS codes on bank one only. I have all new CPS within a year or two. My alt had a bad diode which lets AC volts into the electrical system which Fs things up.
Anyway what I would suggest is charge the battery when the car is not in use. Then see if the cars symptoms stop with a fully charged battery. Full battery resists the AC better and keep as many electrical things off as you can.
 

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Discussion Starter #5
Guys - all coils and plugs have been replaced. Coils on cylinders with misfires were replaced again (even though they were months old). I know that others on here have had the "rough start/first minute or two" of the engine operating and I know that the engine is running closed loop at this point. Many threads on this don't really give the final...."this was the problem". It does also misfire after running.

The alternator runs perfectly in the shop...I think its like 14.25 volts or something? But it could still be bad.

My MAIN issue....is that at one point....the ONLY thing the shop did was update my software and it ran like a dream.....for 2.5 days....then it misfired and back to running poorly.....all the time....not on and off....all the time.

It just seems to me that somehow the engine mapping is getting corrupted in the memory or something?

Any....thanks for the responses so far....I'd love to hear from someone that had a similar problem.
 

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I hate to state the obvious, but computers aren't analog, they either work or they don't. The program can't get partially "lost" or "confused". Maybe you should re-wire the DME with Monster Cables so the electrons can find their way around properly hiha

I have no idea if it is your alternator or not.

It sounds to me like upon the reflash the car ran well and then as the fuel trims changed it stats to run poorly. To me this would suggest bad O2 sensors.

I would reset the ECU and see how the car runs after the reset. If it runs well right after the reset - when no adaptations have occurred - but runs more poorly as the ECU adapts, then the ECU is getting bad information and making unnecessary or incorrect adaptations.
 

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Discussion Starter #7
As I stated before....all O2 sensors are new....all spark plugs are new....all coils are new....vanos new...fuel pump and relay new....MAFS....new.
The whole computer is not a single 1 or 0....have you never had a corrupt file? Never had a bad memory sector? Who knows....there could be a bad connection on the part of the ECU that receives the sensor inputs...don't know. But once is goes bad....its stays bad and doesn't revert to running right randomly.
 

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The alternator runs perfectly in the shop...I think its like 14.25 volts or something? But it could still be bad.
Depending on where they tested that voltage that is not a good number. The regulator should not let it get above 13.8 even though it sometimes gets to 13.9, that is acceptable. The car will drop into limp mode at 14.75 volts because the DME has a desire to see a certain voltage. Those are taken off one of the terminals in the Ebox. Pull up the hidden OBC menu and go to test #9 and watch what it says and report what you see.
 

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Discussion Starter #9
I guess it could be the alternator....but the thing I don't understand is that it runs the best it ever has for 2.5 days on the new software load....then goes back to running bad. I would expect the bad alternator would be bad all the time and wouldn't some how run fine randomly for 3 days?
 
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