What do you guys make of these Data Logs?
#1
01-12-2017, 10:16 AM
Join Date: Sep 2010
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What do you guys make of these Data Logs?
Trying to hunt down loss of power from an otherwise smooth running '05 5.4L 3v with 200k miles. Dealership went over engine and replaced two plugs and a coil (this fixed a highway shutter, but not lack of power). Throttle body and MAF have been cleaned. New Motorcraft filters and oil all the way around. I have attached a few data log photos from last night after doing a PCM re-learn (I just unplugged battery for 30 min).
The numbers not shown include the constant fuel pressure of 40psi throughout the RPM range and idle. The catalytic converters from bank 1 (bank 2 not an option on my scan tool) were about 800 degrees at idle and 1600 degrees at max load.
The downstream o2 sensor on bank 1 will level out around .6V. The downstream o2 sensor on bank 2 will NOT level out and continues to fluctuate with the upstream o2. These sensors are Bosch universal. I moved the sensors around and downstream bank 2 continues to fluctuate.
Note that bank 2 short term fuel trim (STFT) was consistently in the negative with its LTFT well above 5 normally at idle and reaching 13+ while driving. (The first picture is initial startup with LTFT at 0). While driving, you can see both LTFT elevated, but bank 2 is normally over 10.
MAF under WOT was about 18ish, with normal driving around 3. Engine load % was at 20-25% while idle and would easily reach 70-90% while driving in the 40-55mph range. Baro was 91, I do not know how to check that, but I'm in Wyoming at 5,300 feet. Advance at idle was steady at 11ish and normal driving went to max around 33ish.
Does anyone have any input on these number? Thanks in advance.
The numbers not shown include the constant fuel pressure of 40psi throughout the RPM range and idle. The catalytic converters from bank 1 (bank 2 not an option on my scan tool) were about 800 degrees at idle and 1600 degrees at max load.
The downstream o2 sensor on bank 1 will level out around .6V. The downstream o2 sensor on bank 2 will NOT level out and continues to fluctuate with the upstream o2. These sensors are Bosch universal. I moved the sensors around and downstream bank 2 continues to fluctuate.
Note that bank 2 short term fuel trim (STFT) was consistently in the negative with its LTFT well above 5 normally at idle and reaching 13+ while driving. (The first picture is initial startup with LTFT at 0). While driving, you can see both LTFT elevated, but bank 2 is normally over 10.
MAF under WOT was about 18ish, with normal driving around 3. Engine load % was at 20-25% while idle and would easily reach 70-90% while driving in the 40-55mph range. Baro was 91, I do not know how to check that, but I'm in Wyoming at 5,300 feet. Advance at idle was steady at 11ish and normal driving went to max around 33ish.
Does anyone have any input on these number? Thanks in advance.
#2
01-13-2017, 11:06 PM
Senior Member
I do not see as much in the readings as I do in what you said.
That perfectly describes a bad CAT on bank 2 completely consistent with your description of Bank 2 fuel trims running positive and could have resulted in a melted /clogged honeycomb. Restricted exhaust flow will definitely exhibit itself as a loss of power.
Correct the lean condition on Bank 2 ("+" fuel trim) before you replace the CAT or you'll risk just ruining it.
Good luck
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The downstream o2 sensor on bank 1 will level out around .6V. The downstream o2 sensor on bank 2 will NOT level out and continues to fluctuate with the upstream o2. These sensors are Bosch universal. I moved the sensors around and downstream bank 2 continues to fluctuate.
Note that bank 2 short term fuel trim (STFT) was consistently in the negative with its LTFT well above 5 normally at idle and reaching 13+ while driving. (The first picture is initial startup with LTFT at 0). While driving, you can see both LTFT elevated, but bank 2 is normally over 10.
...
The downstream o2 sensor on bank 1 will level out around .6V. The downstream o2 sensor on bank 2 will NOT level out and continues to fluctuate with the upstream o2. These sensors are Bosch universal. I moved the sensors around and downstream bank 2 continues to fluctuate.
Note that bank 2 short term fuel trim (STFT) was consistently in the negative with its LTFT well above 5 normally at idle and reaching 13+ while driving. (The first picture is initial startup with LTFT at 0). While driving, you can see both LTFT elevated, but bank 2 is normally over 10.
That perfectly describes a bad CAT on bank 2 completely consistent with your description of Bank 2 fuel trims running positive and could have resulted in a melted /clogged honeycomb. Restricted exhaust flow will definitely exhibit itself as a loss of power.
Correct the lean condition on Bank 2 ("+" fuel trim) before you replace the CAT or you'll risk just ruining it.
Good luck
#3
01-14-2017, 02:25 PM
