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 !

You can look at the file from the following link:

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

It should open up google docs. From there, if you select File > Download it should let you save it as the original .xls file. V8 or else ...

Can't download from here. IE reports "The website requires a login"

What happened about the inlet air temperature issue I pointed out?

Managed to download this now from a different location & browser. At what point during the run is the error generated?

It doesn't quite get to the point of the engine light coming on on the run I did, but if you look at column C ... thats my long term fuel trim - the base value of adjustment the car does to try and keep the general fuel ratio correct.

It starts out about -0.8% which is good ( i've read that fuel trim should be +/- 10% typically ). It stays the same until you get to about time 16:01.8 and it just starts plummeting ... by the time I'm up at the farm letting it sit at idle, its sitting at -21.1% ( way beyond the typical 10% ). thats a lot of adjustment in the space of 1.8 miles.

Its that plummeting which is what I'm trying to find the source of. Essentially it just keeps plummeting until it hits its limit, cant go any further and throws the error. If its reducing its fuel trim, its thinking somewhere that the fuel mix is too rich and is trying to back it off.

As for the temperature ... on one occassion when it threw the error, it showed a minus value again, when all other times it had been reading positive temps. I wondered whether the pins on the connector were not quite matching / touching correctly. I've since bent the pins slightly so that they are forced against the connector tabs. Not seeing any negative readings so far.

thanks for looking. V8 or else ...

I would suggest to run the car with injector cleaner mixed in the fuel for a bit. I had similar issues with one bank being too rich and knowing (part of) the history of this car (sitting still for two years) it may be gum deposits in the fuel system that cause the injectors to give some extra fuel. Although with me it was one bank (1) and a long term fuel trim of 2.54% as opposed to 0.8% on the other bank.

The only fault i got was the bank 1 too rich so it checked everything and ended changing oxygen sensors and still the problem persisted. Following running with injector cleaner the fault stays away for quite some time now. So I plan to keep running injector cleaner for a few more tanks and then see how it does. May be worth a try since your car has been around for quite a bit so maybe it has similar issues.

Looking at your oxygen sensor values, they are quite different from mine but that may be because yours has the BMW V8 in it. Worth looking at what the values need to be for those sensors. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

I'll not rule it out, but i will say that i seem to ge tthe error on both lpg and petrol ... which makes me think that its less likely to be the injectors. V8 or else ...

I'm going to assume that "sensor 2" is the post-cat O2 sensor, like mine.
at about 16:24, your downstream O2 sensor starts to show crappy values.
When it's working right, upstream sensors should (and do) bounce back & forth, and the downstream sensor should be pretty stable.
Your D/S sensors hold steady, then drop for a while, then go way up.
At about the same time, your trim is dropping like mad.
Sensor 1 is still bouncing correctly.
High sensor voltage = rich.

My 2000 was showing crazy rich on bank 2, enough to throw a code.
Turns out the coil pack was bad; no sparky-sparky on cylinder 8, so unburned fuel was pouring into the exhaust.
On that vehicle, it's a simple matter to pull the plug wire to confirm spark, not so easy on the 4.4 BMW coil-on-plug arrangement.

On yours, both banks are tracking almost the same, which implies identical problem on both banks (which doesn't seem likely) or a problem coming IN to both banks.
So now you're back to MAF maybe.

"after market" MAF might be part of it.
"pins on connector not quite matching" might be part of it, too.

I'd double-check the connections, both at the MAF & in the e-box, if you've been in there poking around lately. Jim
2000 NAS HSE
2005 NAS HSE

Thanks for taking the time to look at it. I'll have a look at the downstream sensor data, although i had glanced at it as I had been under the impression that trim was set by U/S only and D/S was just for the system to check the cats were working.

Quote:

On yours, both banks are tracking almost the same, which implies identical problem on both banks (which doesn't seem likely) or a problem coming IN to both banks.

U/S D/S:
Yes, D/S sensors are only to monitor cat function, all adjustments are based on U/S.
But what the D/S sensors tells us is that it's going so rich, the cats can't keep up.

If you were to monitor less data, the "granularity" on the sensor data would be smaller, so it would be easier to see if the U/S sensors were saying "high" more than "low". But that's not really in doubt at this point.

What was that "bank 3 & 4"? Is that to do with LPG, or do you have a W16 in there?
Pulled it out of your Veyron, did you?

Good luck with the new MAF, & post up the results. I HATE throwing money at the car trying to solve problems...  Jim
2000 NAS HSE
2005 NAS HSE

Jim,

No idea what banks 3 and 4 are ... the software offered it up as available data, so I pulled it all ... just trying to get a full picture. I know that some ECU's will split an inline 6 cylinder into 2 banks ... so I wonder whether the ECU shares some of its functionality with an ECU that would run the larger BMW 5litre V12 engines ... and whether each bank of 6 gets split ... hence 4 banks. there is probably merit in that since the V12's have a pair of throttle valves.


Anyhooos ....

The genuine MAF sensor from LR ....
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//// drum roll
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works.

Plugged it in, reset everything. took it for a drive, and it seems to be running as sweet as a nut on both petrol and LPG. Adaption values aren't too bad, U/S O2 readings are bouncing above and below 0.45 and the lambda reading is staying between 0.98 and 1.02. Finger crossed its going to stay that way. On the run I did, I could tell that it was pulling better under load, after the first settling in of a few hundred yards acceleration, everything after that was super smooth across all the gears and pedal positions.


What was different then between the 2 MAFs? The actual air flow reading. At idle,

- the after market MAF was reading 20 to 24 kg/hr.
- the LR one was reading about 16 kg/hr

Which would explain the rich running. Aftermarket MAF tells car more air is entering engine, ECU adds more fuel for air which isn't there and so runs rich.

The aftermarket MAF was giving me a reading and its readings were proportional to the throttle position as expected, just that it was the wrong amount. Unless you know what it should be reading ... then you would think the aftermarket one was working correctly.


So hopefully thats it sorted. I'll posst back after a few days and see how things are. I may try and put something up for the wiki for others further down the line so that others dont make the mistake I made ... or can use the info to help diagnose their own engine. V8 or else ...

Good news.

I think the answer to the banks 3 and 4 question is that there are actually 4 lambdas because there are two cats since it's a v8 engine. So you need to be sure that 1 & 2 are the pair of pre-cat sensors rather than 1 & 2 being for the first bank and 3 & 4 for the other bank. I don't actually know which way they are organized.

I understand what youre saying ... but the software lists the O2 readings as
bank 1 - sensor 1
bank 1 - sensor 2

bank 2 - sensor 1
bank 2 - sensor 2

And then you have long and short fuel trims for banks 1 to 4
and no O2 readings for banks 3 and 4.

( and the software that generated the file is generic ODB2 software... its an industry standard naming scheme ) the names also match the readings from the faultmate diagnostic kit I have as well.

I personally think banks 3 and 4 are redundant and a legacy of common components / functionailty / programming of the ECU's for different engines. V8 or else ...

Yay new MAF!
And, since the aftermarket one is an "electrical" part, you can't return it, right?
arg.

Throw it on the shelf as a spare. If your good 1 drops dead, at least you can use that one to get around while you wait for the proper replacement to arrive.
I have a set of front & rear airsprings for my P38 like that.
They're old, they leak to empty overnight.
But in a pinch, while I wait for replacements to arrive, I can use them.


For the wiki, the most useful data would be the actual airflow, i think.
Like what happened to you; unless you know what it SHOULD be, there's no way to know if it's right...
That almost seemed easy.
 Jim
2000 NAS HSE
2005 NAS HSE

my generic reader can read up to 4 O2 sensors on each bank.
i only ever look at the first 2, and even then, if i want to see the fastest response, I only look at 1 at a time.
The less things the reader has to read, the faster it can repeat the loop. Jim
2000 NAS HSE
2005 NAS HSE

fisha wrote:

bank 1 - sensor 1
bank 1 - sensor 2

bank 2 - sensor 1
bank 2 - sensor 2

Bank 1 is the LEFT (odd cylinder) bank
Bank 2 is the RIGHT (even cylinder) bank
sensor 1 is upstream of cat
sensor 2 is downstream of cat

Left and Right from the driver's seat.
Even for you guys who steer from the wrong side of the car.  Jim
2000 NAS HSE
2005 NAS HSE