Help understanding this idle log

[efizjb]

I know there's plenty to critique here. The main question I have is how can the fuel trim only show -1.6 yet how at frame 50-64 d 93 to 110 how can the O2's read like there is no fuel at all?

I know I need to fix the 400RPM row to help fix this dip. Any other suggestions please fire away!

But O2's would say I need to richen up idle cells but trims say otherwise?

[joecar]

You log shows that the O2 sensors are switching at 10 second intervals, this is way too slow, how many miles are on the O2's...?

[WeathermanShawn]

Yea, those O2's look hosed..

Where are the O2's located (headers, etc..)?

[efizjb]

Thanks guys. They are not that old at all, probably less than 6K on them. I've got SLP longtubes and they really seem to plague cars with the 1133 1153 switch codes. They are the Bosch Corvette rears. I've been searching for switch point threads, but nothing is realy clear on how to determine where to set them. I've read by a few to set to 450-500 range, but then when I opened the table, I didn't quite understand there were different cells, as opposed to one switch one point. Being at work I don't have it in front of me, but I think there were diffferent CL areas and didn't know which ones to change.

Should I change the O2's and any recomedations on switch points before relogging?

oh, and yes the SLP O2 bungs are way back there....

[WeathermanShawn]

It must be an issue with that header and/or location. I have the same type of O2 sensor you have and so far have 25K on them with no issues.

As far as the switch-points, its more of a tuning preference to set them all to 450 mv. It can make LTFT tuning a little more predicable. I have used anywhere from 450-550mv for tuning purposes.

In your case, that it really not the issue. Perhaps Joecar can comment on why they are toast after only 6k. Could be location or wiring.

You definitely need them operating at peak efficiency. Changing them would be a first good step.

[efizjb]

Yeah, I think they're not hot enough. I did find one post that with less heat the operating range of a NB was "narrower", and that lowering the switch points would help, but there's not a lot on the subject, and I didn't want to change based on one thread without much suppoting posts. I really don't want to wrap the headers but might have to.

I can swap them out and relog.

[joecar]

They might not get hot enough and/or might have gotten carbon fouled... pull them out and inspect them, you may be able to clean them by spraying with MAF cleaner.

[efizjb]

Thank you. I'll report back after cleaning them up if successful or replacing