WB O2 says lean, pcm says rich?

Wideband says I'm lean at steady state cruise. The gauge is reading 15:1 AFR or higher and I'm seeing the same with the analog input hooked up to the MVPI.

However, the STFT numbers are showing that the ECM is subtracting 15-20% fuel at the same steady state.

I replaced the wide band sensor since the original one is 6 or 7 years old now but nothing changed.

what am I missing?

the o2 sensors are in their original place?

They are not. The car has long tube headers. I started from the tune that was in the car last year, which also has long tubes, but I just assumed that the guy doing the tune adjusted for the headers.

It turned out to be that I never forced the ECM into open loop. I changed the table, but never wrote it to the ECM.. ugh.

See my PM back to you. You shouldn't need to force these cars open loop to tune them. My suspicion would be that you've got a problem of another sort. In the end the on-board WB sensors will be controlling the fueling so you should be using them their feedback to set your calibration. If you can't make the two agree (on-board versus external) then there's a problem somewhere.

Quote:

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Originally Posted by jchambers

See my PM back to you. You shouldn't need to force these cars open loop to tune them. My suspicion would be that you've got a problem of another sort. In the end the on-board WB sensors will be controlling the fueling so you should be using them their feedback to set your calibration. If you can't make the two agree (on-board versus external) then there's a problem somewhere.

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Could you explain how to do this?

The car is a 2007 Mustang GT. I should have included that in my post. No factory widebands.

That changes things. Have you checked to make sure that the sensor connectors haven't been swapped side to side? That'll cause what you describe. A log and tune file would help.

As I mentioned above, it was a problem only because I was trying to tune in open loop, but never actually wrote the OL TPS thresh table to the ECM to force OL.

thanks for the replies.

Just to close the loop on this.. My AEM wideband analog output was reporting incorrect voltage. I have replaced the controller and all is good now on this front. I did a lot of reading online and have found various accounts from others struggling with the analog output from the AEM product. The gauge read fine, but the output was off and was very difficult to try to find a correct voltage offset for.