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Why am I suddenly running lean at idle?

Old 09-19-2007, 09:05 PM
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Default Why am I suddenly running lean at idle?

I have been working on my tune for a while with EFI live and a LC1 wideband. I have done 3 passes of AutoVE for "normal" driving and the AFR has been pretty much dead on at 14.63. I have not yet worked on PE or WOT tuning. I have been working on getting all of the surge out of it first, and making some good progress. Tonight I spent a couple hours working on the throttle cracker and decay. Without changing anything but the TC and decay, it suddenly started running lean at idle, between 15 - 17, with some spikes to 19. And I've started to pick surge back up in areas where I had it tuned out. So I don't think it's the WB but I guess it's possible. When I pull up the BIDI controls and command it at 13.5, it only drops down to about where it should be 14.5 - 15.5.

Does anyone have any idea what is going on and how I can get it back besides AutoVE again? Or do I need to do this if I add a bunch of air to the TC anyway? I can't see why but I'm still learning and could use some advice. My drivability has improved greatly and I don't want to take (another) step in the wrong direction.

Thanks in advance.

Dave

Edit: I'm still running closed loop/SD by the way.
Old 09-19-2007, 10:07 PM
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Sounds like some of my tuning experiences lately...I have ordered a new sensor as I think I was chasing my tail. I finally started listening to the engine and said to heck with the sensor until I get the new one.
Old 09-20-2007, 09:45 AM
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With headers the wideband and the narrowbands may diverge
at low exhaust flows because the wideband is heater-controlled
and the narrowbands are hope-the-heater-works. Was the
weather colder than before? External changes can't be ignored
especially with a speed density only setup. The IAT (and its
realism) factor into it strongly, especially as it swings away from
where you initially tweaked it up.
Old 09-20-2007, 11:13 AM
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It was colder when it went lean than it was when I did the VE table, so maybe it is the weather. I thought as long as I was running closed loop it would adjust even if the maf wasn't hooked up.


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