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Discussion Starter #1
Hey everyone. Alot of people seem to be having problems with their air/fuel ratios, a lot of things can throw these off. Some might not even know and can loose some performance. Doing this simple yet effective test with the M5 brought me here. There were a few threads on this topic so why not make another, might help out someone in the future. The more the better. Right, So after doing the number 4 test on the instrument cluster i was getting lower readings than what it should be. 80-100L/H at WOT to redline 3rd gear. No SES, car runs smooth, but does seem to be running rich. Then decided to do some diagnostics to point me to the right direction. The INPA and PA software did pick up a MAF error ( courtesy of Rob ) i have attached pictures of fuel trim and 02 sensor readings. Can anyone colaborate what these numbers mean exactly? And whats off here? I already ordered both MAFs and pre-cat 02 sensors.Thanks alot.







The last picture shows the car idling for a while now. Readings of the adaption value bank 1 and 2 are further off.

 

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It's quite rare to get a code for a bad MAF. They have to get pretty bad to bring it in. The DME knows when they go bad because the air flow they are reporting doesn't match the throttle opening, rpm, and IAT.

Ignore the hex 10 shadow code. Everyone seems to get that one in PASoft.

I show "Engine noise too high", aka "Knock Control Deactivated/Knock Protection" for code 8C, rather than the "Internal fault" PA Soft shows, although I suppose it could mean internal fault in the engine. Is the engine making pinging or knocking noises (eg VANOS) that might be confusing the knock sensors? Anyway, being a shadow code, you can ignore it until it comes in as a hard code.

The INPA data is interesting. It shows the DME is controlling fuelling/AFR OK since the lambda integrators are both close to 1.00, but to do that, it is having to pull a lot of fuel from bank 1, shown by the additive adaption being unusually low at -0.29. This means bank 1 wants to run rich at idle. It is also pulling fuel from Bank 2 but the value for that bank is in the normal range.

Since a MAF problem would affect both banks equally, this seems to mean you have an additional problem with bank 1. It's quite rare to have a single bank running rich. About the only things I can think of are the O2 sensor reading false high (in other words it's not really rich) or an injector leak on that side.

It will be interesting to see what happens with the new MAF's and O2 sensors. I suspect they will fix the problems.
 

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Discussion Starter #3 (Edited)
It's quite rare to get a code for a bad MAF. They have to get pretty bad to bring it in. The DME knows when they go bad because the air flow they are reporting doesn't match the throttle opening, rpm, and IAT.

Ignore the hex 10 shadow code. Everyone seems to get that one in PASoft.

I show "Engine noise too high", aka "Knock Control Deactivated/Knock Protection" for code 8C, rather than the "Internal fault" PA Soft shows, although I suppose it could mean internal fault in the engine. Is the engine making pinging or knocking noises (eg VANOS) that might be confusing the knock sensors? Anyway, being a shadow code, you can ignore it until it comes in as a hard code.

The INPA data is interesting. It shows the DME is controlling fuelling/AFR OK since the lambda integrators are both close to 1.00, but to do that, it is having to pull a lot of fuel from bank 1, shown by the additive adaption being unusually low at -0.29. This means bank 1 wants to run rich at idle. It is also pulling fuel from Bank 2 but the value for that bank is in the normal range.

Since a MAF problem would affect both banks equally, this seems to mean you have an additional problem with bank 1. It's quite rare to have a single bank running rich. About the only things I can think of are the O2 sensor reading false high (in other words it's not really rich) or an injector leak on that side.

It will be interesting to see what happens with the new MAF's and O2 sensors. I suspect they will fix the problems.
Thanks for the post! The engine makes no noises whatsoever, and seems healthy (only 70k) I think the shadow codes could be old codes that once came up but were taken care of, maybe by previous owner. Most of what you say makes sense, but if only one MAF is acting up ( says right side ) that means only bank 1 should have bad readings not both like you said i assume? Bank 2 value is ok maybe because the other MAF is fine? Please help me understand. I will do more readings when i get the MAFs and 02s changed. Thanks!
 

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The air passing through the MAF's feeds into a common plenum so MAF1 doesn't specifically measure the air flow to bank 1. The DME adds the two MAF readings to get a total air flow into the plenum.
 

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Discussion Starter #5
Ok gotcha, i hope this an easy fix then :)
 

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Take occasionally the shadow error codes too seriously. I had a while back problem for the rev limiter entered the car in safe mode.
when I read and saw the same code as you.
I then replaced the crankshaft sensor and my problem was solved.
So you only got the shadow codes and never got a had code?
 

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I dunno, I have had that shadow code since I got the car over 3 years ago with no problems, and I've seen it on many PASoft screenshots posted on here. I guess even a stopped clock is right twice a day.:blink:
 
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