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Discussion Starter · #1 ·
Can anyone help diagnose the following datalog file for the RR running rich?

Tearing my hair out with this one.

Since replacing the MAF, I just cant get it to stop coming up with the error of both banks running rich. I bought an after market new MAF, I've tested for intake leaks and I've cleaned the throttle butterfly area as much as I can ... I'm going to pull the spark plugs tomorrow, but I'm at the stage of going out and buying a genuine just to see if its the MAF thats the problem.

But before that, I thought I would share the following data log file to see if anyone else can spot anything obvious thats causing the rich running.
The file linked below is about 20 mins of datalogging done via a generic OBD2 scan tool. It was the only way I could get all the data into a single page ( The faultmate only shows selections of the data at a time ).

Immediately before the logging started, all the error codes from the engine were cleared AND the fuel trim adaptions were told by the faultmate to reset ( you can see that to begin with the fuel trims on bank 1 and 2 are basically zero)

Car was then started up and the following file logged over about 20 minutes. The run involved driving along the road to the farm.
Essentially a short hill out of the street,
then a gentle uphill country road (2 miles max )
sitting running at idle for a good while whilst the horses get fed
drive back down to the house.

If you look at the fuel trims ... they plummet ... but i cant obviously see why. Looking at the rows where the fuel trim plummet, there is no obvious major change in the other readings which I can see correlate to the drop in fuel trim.

Anybody got any insights / ideas would gratefully be appreciated ... a lot ! :)

A zip file containing the .xls file should be attached to this post, if you cant see it, then you get the file from the following link:

https://docs.google.com/open?id=0B9zseqKHBN7sRUU0ZENrMzVwSXc

It should open up in google docs. From there, if you select File > Download it should let you save it as the original .xls file to your machine.
 

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2006 RR HSE/White/Tan; 2010 LR4 HSE/Silver/Black; 2012 RR Supercharged/Silver/Black
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Re: Can anyone help diagnose the following datalog file for the RR running rich?

I bought an after market new MAF....
End of story. The BMW ecu is very sensitive to sensors. I once replaced my cam position sensor with an aftermarket after a failure, two days later it was throwing the same code. Bought a BMW unit and fixed it permanently. Went online and discovered that everyone has the same issue with aftermarket brand sensors.

If you go to bimmerfourms.com you will read that e38/e39 owners with the same m62 engine as yours routinely report that aftermarket MAFs do not work properly and are a waste of money.


http://forums.bimmerforums.com/forum/showthread.php?t=1691436&highlight=aftermarket+maf

"
NOTE: Never, EVER, EVER put aftermarket MAF's in your BMW
[HR][/HR]Yeah, I know, I know, all you guys already know this and there have been ample warnings on this site and others (Wait! There are others?) to steer clear of aftermarket MAFs and especially the ones on eBay and especially for the V12.

Well, about a year or so ago I knew I needed new MAFs (lots of misfires and such that went away when I cleaned the MAFs but then came back). However, the new parts list for $410 each and, as it is with many things in the V12, I needed two of them. Even shopping around, I was going to need $500, which I didn't have at the time.

SO....., I compromised and put in two cheap ones off eBay for $150 instead. (No labor - a three-year old could do this job in 5 minutes flat.) My problems seemed to go away, sort of, but eventually came back in other forms than before: misfire codes, MAF codes, ignition system codes, hesitation, and clear indications that the car was running on only 6 or 8 cylinders (horrors!) and then suddenly kicking in with all 12.


I was growing very tired of the SES light and was close to taking the advice of Tom and Ray from CarTalk and putting a piece of black tape over it.

I had it to the indy and yes, they found one of the right O2 sensors was bad and, on a subsequent trip, the other right 02 sensor (did I mention there are 4 of those?). The SES light went out and the car drove well for, oh, a half day, before it came on.

Finally, I broke down and purchased real Bosch MAFs, two of them, from http://www.carpartswholesale.com for $260 each, minus $52 from a 10% off coupon I found online, plus $26.60 for two-day shipping. I eventually got my $26.60 back after CPW shipped me only one, instead of two, MAFs while charging me for two, though it took me another week to get my part (another whole horror story). Still, I had to spend the best part of $500.

Well, I finally have my car back. Drives like a dream, pulls like train, and (aside from the 02 sensors, which really were bad), the fault lay with my cheap-ass eBay parts. I probably spent the money I originally "saved" and then some before I learned this lesson.

I am now tooling around town with a grin on my face burning $4/gallon gas a prodigious rate and putting my new summer tires to the test. The new drive shaft CSB, giubo, and transmission mounts (separate post) certainly help the fun factor too.

So, take it from me, NEVER, EVER, EVER, put aftermarket MAFs in your car. You have been warned!"
 

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Discussion Starter · #3 ·
Re: Can anyone help diagnose the following datalog file for the RR running rich?

Thanks for replying.

I've bit the bullet and am about to head down and pick up a MAF from the LR dealer and I'll see how that goes.

I bought the aftermarket one based on advice from a mechanic chap I know. He said that he generally bought the best aftermarket part he could, not the cheapest, just the best after market one. From my experience and what you've posted, it looks like a wee lesson learned.

Will post back on how it goes.

Don.
 

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Discussion Starter · #4 ·
Re: Can anyone help diagnose the following datalog file for the RR running rich?

Well, back from dealer. Genuine part fitted. Car now appears ( will monitor for a few days yet ) to be working properly again.

The difference between the 2 was the amount of air each MAF was registering. At idle, the aftermarket one was reading about 20 to 24kg/hr ( ish ). The genuine MAF is now reading about 16 kg/hr. So with that in mind, it explains the rich running. The engine was being told more air was entering the engine than actually was, and as a result was adding fuel to the mix for air that wasn't present ... hence the rich running.

The aftermarket one was working in that it was giving an air flow reading proportional to the throttle body position ... just that the readings were out from what they should be.

Lesson learned in this case = when it comes to sensors like that ... buy genuine.
 
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