I just replaced my pre-cats on my 4.8is. Going to have to find that fuel adaptation reset menu in the Foxwell.

What is this fuel adaptation and what is foxwell? I've never heard of having to do that. Also, I didn't have pre-cats on mine, just the two off the manifolds.

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The Foxwell is the name of a diagnostic tool. Foxwell NT-510 is a good one to get and you can buy it for less than $200.00 USD and you can read and correct almost any errors in the BMW. Taking the X5 to the stealer for a read and resetting of any error codes (not including parts) can run $200-$400 so it's a wise investment and it can also reprogram some systems/items.

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Sorry, should have been more clear. I meant pre cat o2 sensors.

And what eodguy said regarding the foxwell.

So is a fuel adaptation reset something I should have tried? Nobody had ever mentioned that to me before.

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Yes apparently after replacing certain components the computer needs to be told to start over. The long term fuel trims are saved between starts in the DME. I forgot to take a picture of the before values. I had a pretty solid mismatch in short term trim values like one was 5% and one was 2%. They were not large values.

The long term trim however may have changed a lot because those were in milliseconds and may have dropped a decimal! Eg. From 0.02 Ms to 0.005ms.

I'm any event I couldn't believe it was working and check for pending codes every 20-30 minutes on my 90 minutes drive home and no code! Imagine my relief after two weeks of every start getting fuel adaptations lean code about 3 miles into my drive.

INPA software can do the fuel reset but I was sure hoping foxwell could and there is a "reset adaptations" in the DDE module I can't remember if it was in the control or maintenance section but it did the trick.

I'm still not 100% convinced because I only have one long drive since I did the process but after 20+ SES over two weeks and no code for 75 miles drive, combined with a 20-25% bump in mpg (from 19-23) I'm pretty sure that's what it needed.

I'm still getting a small weirdness in the trims (long term neg short term pos) which is said to be an indication of failing MAF which was the next hardware tweak I would be doing.

I will probably swap mine with wife's to see if anything changes.

Some cars will reset DME adaptations by unplugging the fuse in case you didn't have a scanner that can, but I don't know if E53 is one of those cars.

Cat replacement
 

Oh: the primary feedback that chamged was that the post cat sensors would rarely if ever get below half a volt averaging 0.7 or something. Instantly after the reset they would get down to 0.1 for solid seconds at a time and average close to half a volt as I believe they are supposed to.

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This was while stopped using on/off throttle to force a swing. Good to see both banks working in unison.

The secondary instant feedback was that the fuel consumption improved hugely: 20-25% improvement! Funny how running lean makes you consume more fuel that's irony for you.

I think I'm about to just throw some regular cats back on, not trying to deal with this headache.

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Oddly enough, 1k miles later my engine light is now off...

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Long road trip? Maybe the truck did it's own adaptation reset? :) It's nice (and rare) when problems fix themselves.