I've been noticing at certian speed my AEM wide band is reading around 16:1 at cruise. Then at other times usually on surface streets around 45mph, its reading 13.4:1. Thought my STFT or LTFT were just way off, but I've spent a good amount of time getting my VE and MAF curve dialed in. So today I was driving around and logging. If you look at the attached log, about 10 seconds it, you see the lean cruise, AFR is about 16:1 and Air-Fuel commanded is about 16.00 on the nose. I wasn't logging the stock O2's but there is no reason to think the AEM isn't accurate especially when that's what is being commanded.
I'm not a newbie to tuning, but I can't figure out what multiplier or table could even be involved in leaning it out 8%. It's not in this log, but in another I confirmed it's in closed loop normal fueling mode.
Its a P59, DBW, I don't have flex fuel enabled, no codes. I did turn on EGR for the wide band logging, but still all the fuel tables I can think of are zero'd out. It has an LS3 throttle body with a Torque Rush xlink. Never messed with lean cruise. Segment swapped for the 4L80 a long time ago. I did change to a card MAF, but IAT and MAF curve was re calibrated and read normally. Neither would command 8% lean than what I can tell. I've compared it to the stock file and nothing stands out. The car runs smooth when it's in lean cruise and doesn't. Maybe this started after the MAF conversion or the EGR/wideband mod. Can't say for sure. Anyway here is a log and tune file. Would be cool if we actually stumble on a way to do a lean cruise. v11_2.hplLTD_50lb_TBSS_90mm_EGR_100mmMAF.hpt
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