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also have you been able to to get a log with the 02s reversed?

oops, just saw you posted it.....

i will look at
 

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that log is not long enough and not on a hot engine

i am not getting any long term corrections........

to make these logs useful i need to see changing long term trims, far more important than short
 

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Discussion Starter #83
I'll check if my mechanic has the diagnostic tools necessary. Are we basically needing an oscilloscope?
I'll re-do the reversed bank test tonight after I get some movement in the LTFT's.
Can you help me understand why LTFT's are more important than STFT's?
 

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The job of the long term fuel trims, is to get short term fuel trims to 0

Short term are constantly changing, as per ecm driving them

Long term gives us info on what one bank is trending

And acts as confirmation post repair

If we have a long term at its limit, a CEL is triggered

We make the repair, to validate the repair, we watch the long term correct in the opposite direction
 

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Scan tool

O-scope and or, ignition analyzer

Looking at secondary wave forms, gives great insight to what is happening in the combustion chamber
 

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Discussion Starter #86
This is the oddest log yet, the car starts off with each bank out of wack, then levels out. I confirmed that the banks are swapped, and bank 2's sensor is going to bank 1 in the ECU and vice versa. I spent a few hours verifying the wiring on Sunday so I'm pretty positive of that.
Anyways, here's the log: https://docs.google.com/spreadsheets/d/104aAcWuo4F4h2QC2u4lBXJCbXbxrjZe-EB8NEk1b6m0/edit?usp=sharing
Some things to not in the log, when the fuel trims leveled out, my wideband sensor (not in the log) was reading around 11.6-12.2. Under any sort of throttle, one bank would lean out and the other would go rich. During the log, under no throttle, the car would do a small rev and the banks would level out.
 

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now correct the 02 sensors and do another warm engine log

so we can compare, do not disconnect the battery
 

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Discussion Starter #88

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i have question, i should have asked near the beginning

Is this a stock v-6 engine?

why does it sound so choppy in the vid?
 

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Discussion Starter #93
This is not a stock v6, it has a lot of engine modifications done to it:
stroked and bored to 4.3l, forged internals, ported throttle body, ported upper and lower intake, ported heads, larger valves, decent sized cam (.54/.54), longtube exhaust, and your typical CAI.

The only thing that changed between when it worked and then started doing this is it sat for around a year being started occasionally (except the last 3 months), I took it in and had the timing chain and components replaced, at the same time they threw on the ported upper and lower intakes as well as throttle body. With that in mind, I've been working with the tuner who made changes for these mods but the issue came up. Two weeks ago I tried the previous tune from before the recent changes and the car ran exactly the same way.
 

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so it ran fine before the timing chain work not after?

there is a misfire in #1? I thought it was #4?

The last log is consistent with the ecm using substituted values.

bank 2, is identical to bank 1 now, that is very rare unless the ecm doesn't like what it sees on the 02

it will ignore that 02
 

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Discussion Starter #95
Correct, it ran fine before the timing chain was fixed but not after.

The misfire was in 4, but now after I did the long log with the O2 banks swapped cylinder 1 was about 270 and cylinder 4 was about 380, which is around the same temp as the other cylinders. It's just weird and doesn't make sense to me.

I'm going to test another ecu (same year, model, and trans) and see of that changes anything. Do you have any suggestions on what to look at next?
 

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Discussion Starter #98
The new ecm came in today, thankfully it has the same ecm code and strategy so I was able to flash the tune on it and try running the car. Unfortunately it ran exactly the same as before.. I'll try to get a long log of this ecm if anybody wants one, but I feel like I'm sol at this point.
 

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we are at the point where you need a real scan tool that can look at 02 voltages and other pids

as well a scope, that can look at signals with resolution

it is very possible a mechanical issue is the problem, especially after you say this happened after a major repair
 
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