AFR difference between the banks

Jordo!

That all sound spot on -- I wasn't entirely clear on whether there was a real open or closed loop like there was on narrow band O2 controlled AFR's, because, yeah, as you noted, uprev doesn't clearly indicate it. I thought since it had wide band (5 volt?) sensors it just maintained a close loop throughout, maybe forcing the ECU to trim to stoich under low load.

So is there an aggregated LTFT from the closed loop sections of the map that carries into open loop?

Also, what approximate TPS or MAF voltage switches it over? I'm guessing it corresponds to whatever point in the main AFR target map it goes richer than 14.7?

Is that much variance common on an OEM set up or is this strictly due to the plumbing differences for your set-up?

The only other thing I can think of is that one of sensors may just be reading very differently. Have you swapped the sensors to see if the bank difference moves with it?

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Mitco39

Yes I have found that manually setting the correction tables to some very wrong values (lets say removing 30 percent to the constant throttle section) caused the STFTs to constantly sit high until the LTFTs started to take that into account and change to meet the needs of the STFTs. Needless to say you can be way way out to lunch on your correction tables and the ECU will bring it back into check, it will just take longer to do so. And I guess if you bottom out your LFTs then you will get the rich or lean bank codes from there.

It seems like anything under 14afr commanded will put the car into a closed loop situation although its really hard to pinpoint weather its load based or just afr based. With the BP kit as soon as the boost starts to come on its already in open loop and then that is where you can see how your correction tables really come into play because now the ECU is not looking to adjust these values and it just takes it as "correct".

I have looked on many other forums (including 350z and titan forums) and it seems like its a fairly common issue. I am surprised infact that more people have not noticed it. On the forums I did find people were describing the exact same situation however most of the replies were uneducated and telling the OP to check for boost leaks ect. No boost leak or exhaust leak is going to tell the ECU to inject more fuel if it is already running rich.

As far as switching the sensors on the bank, that wont fix anything because the ECU clearly sees bank 1 is running rich. I can see it through uprev. Its sitting at around 13.8-14.2, yet the ECU is trimming like it is running lean.

I have come across a post where some guys have said disconnecting their downstream 02s have helped to fix the problem. The thought is that the ECU is looking to see a certain AFR post cat, since the cats are gone its getting fooled and I would suspect that the ECU may be injecting more fuel to try and light off the cat or heat it up to bring #2 O2 into whatever reading the ECU would expect to see on it. Unfortunately we cannot see exactly what these 02s are doing. I am going to try unplugging both O2s next time I am under the car and remove the associated codes and see what that does to the tune. Some have said it will force the ECU into a open loop situation under all conditions. One way to find out.

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Jordo!

Switching to open loop is probably both TPS and load based -- the boost just reads as high load (i.e., higher voltage on the MAFs), so the only concern would be if you skew lean under part load with moderate boost. If it's not happening, then I guess its either just load based or weights load as more important than TPS?

As to the 2ndary O2's, I thought if you turned off the DTC for it that effectively got around the ECU taking notice of their presence and attempting to correct -- meaning, you first have to work your way through the the trip detection logic algorithm and then the ECU starts correcting, so if the detection logic is never invoked, the problem is circumnavigated.

If not, and if there's no way to just shut them off or change their threshold, then I bet a lot of us are driving around with weird random fuel trims...

As to switching the MAF sensors -- are you saying voltage readings are the same? If not, it could still be referencing different cells in the fueling map, or if it just aggregates them when accessing the tables, one might be skewing things off more than it should.

On that note, if the MAFs are fine, what about the primary O2's?

Good luck with the 2ndary O2 fix!

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