Tune Going Lean - Out of The Blue???

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Aug 7, 2012 | 12:27 PM

hiltsy855

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Tune Going Lean - Out of The Blue???

'02 Camaro, specs in my sig. I did my own tune a couple years a go with EFI Live and I was pretty happy with the results. I have an LC1 wideband with a display so I can see A/F ratio. It didn't always lock in at 14.6 but would maybe vary a few tenths up / down, no biggie. But out of the blue last week it started going real lean on cruise, idle, everything, and it jumps all over the place - maybe 14.0 all the way to 17 - averaging 15.5 or so. I re-calibrated the LC1, still the same on the display and verified by EFI Live. I don't get a check engine light and I can't find a vacuum leak. LTFTs are +10% or so which verifies the lean condition. WOT seems good and the A/F goes to 12.2. and stays there. Can you guys suggest some things to check? Do I have a bad O2 sensor? Thanks in advance.

Aug 7, 2012 | 12:38 PM

SSpdDmon

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Could be a vacuum leak, exhaust leak, bad sensors, dirty MAF, or maybe a coilpack that's on its way out.

Aug 7, 2012 | 03:43 PM

jimmyblue

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From: East Central Florida

A misfire can also jack the exhaust oxygen content, and
the fuel trims that follow it. Might see if you've got anything
showing there.

Aug 9, 2012 | 08:22 PM

hiltsy855

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From: Iowa

Ok, I'll do some more checking. I know I don't have any exhaust leaks, not audible ones anyway. And wouldn't a misfire make it go rich not lean?

Aug 10, 2012 | 07:42 AM

Old Geezer

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Fuel psi is?

Aug 10, 2012 | 10:23 AM

hiltsy855

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Quote:

Originally Posted by Old Geezer

Fuel psi is?

Good point. I don't have a gage installed, I probably should get one. The odd thing is I get 12.2 as commanded at WOT.

Aug 10, 2012 | 11:27 AM

Mike@Diablosport

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commanded will always show what your tune is commanding, if you're AFR used to match the commanded AFR, and noes not any longer, then something on the car has changed...

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