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Old 10-26-2015, 10:14 AM   #1
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Default AFR bouncing all around

Hi All,
I just started having this issue, Nothing has really changed, I've loaded older configs onto my MS3 just to see if it was a tuning issue, issue was still there so I reverted back to my current tune. AFR are stable during idle, engine feels fine, not jumpy or rough. Just don't want to ignore it. Has been running great for a few years. This video is just light cruising, no load, 4th gear. I'll post a log soon.

2004 MSM
MS3 ECU
775 FIC injectors,
2560R Garrett
BEGI S4 Manifold (new style)
Artech exhaust,
Turbosmart Bypass

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Old 10-26-2015, 10:15 AM   #2
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what does your MS3 log show?
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Old 10-26-2015, 11:21 AM   #3
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I've had a similar issue that was resolved by decreasing the authority on EGO correction. It seemed to be over-correcting AFR's resulting in it oscillating between rich and lean.
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Old 10-26-2015, 11:29 AM   #4
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I've had this issue with a noisy TPS signal causing tps-dot to be high and triggering accel enrichment when it shouldn't have been triggered.
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Old 10-26-2015, 01:04 PM   #5
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Quote:
Originally Posted by pdexta View Post
I've had a similar issue that was resolved by decreasing the authority on EGO correction. It seemed to be over-correcting AFR's resulting in it oscillating between rich and lean.
Same, mine was set at 25, or something crazy, dropped it down to 15. Also double check your AFR table and find out if you're using "Incorporate AFR table" or not for your fueling.
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Old 10-26-2015, 01:07 PM   #6
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IF the issue randomly appeared without changing anything then it's not a tune/ego issue
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Old 10-26-2015, 01:11 PM   #7
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Ah, maybe dead sensor? You say the car runs fine.
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Old 10-26-2015, 02:19 PM   #8
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Car seems to run fine, with the exception of a cold start issue I've been hunting down for about a year.

Here is a log of a drive at lunchtime.
Attached Files
File Type: msl 2015-10-26_12.46.28.msl (2.78 MB, 87 views)
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Old 10-27-2015, 09:47 AM   #9
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Would a bad injector cause something like this? I t idles fine, but as soon as any load it put to the car (even just holding the rpms at 1900 while the car is stationary) causes the AFR to jump around. I've checked everything I could, used older tunes to make sure it's not a tune issue.
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Old 10-30-2015, 09:58 AM   #10
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bump?
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Old 10-30-2015, 10:05 AM   #11
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Quote:
Originally Posted by tuckermon View Post
bump?
Is your injector PW moving around with AFR changes?
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Old 10-30-2015, 10:44 AM   #12
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no, the pulse widths are steady.
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Old 11-06-2015, 09:07 PM   #13
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Ok, so answer time. I took a chance and figured the O2 sensor was bad. I talked with AEM with zero help, they actually gave me a replacement part number that was 30-2004 (don't buy this). I ordered the sensor online and it did not have the same plug connection. I called them back and they told me that it was a 50/50 chance of the sensor and that the other part number was 30-2001. I then ordered that sensor ($80). While doing some research on the 30-2001 part number, I found out that it's the same as a Bosch 17018 O2 sensor ($55). I ordered a 17018 sensor as well and I confirmed that the 30-2001 sensor and the 17018 are the same. I installed the 17018 sensor and everything is back to normal.
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