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Thread: Economy and Lean-return-to-idle questions

  1. #1
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    Default Economy and Lean-return-to-idle questions

    Today I had some time, so I changed my AFR for e10 from what I was using 14.22 to 14.42. Thought maybe 14.2 was a bit rich and our gas is 'up to 10% eth' according to the stations. So stock was 14.68 on my truck. I figured I would bring it up a notch since my best milage has been 16.2 and I was getting 16.5 beofre. However, maybe I was getting better because of the 'winter' fuel blend. Now summer is here we have 'summer' blend. So could be that was the difference in my economy going down some?

    After I reflashed the PE Ratio change and Commanded AFR change, I noticed while I was idleing in neutral, my AFR went very lean (17's). Gave throttle and came back up, but went lean for a minute after let off. Drove fine and AFR was toggleing as usual. PE came on as usual. But when I pulled to a stop and idled, it went lean again. Did it 2 more times after a drive and coming to a stop. Is that normal until it relearns to go so lean when coming to a stop after a drive. After a minute it goes back into normal idle afr :( weird

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    Noticed today that when I start up and idle, I get a steady 14.6 while it warms up. After it idles down to curb idle, it fluctuates. But within a normal range. According to the AEM WB digital gauge, I witnessed 14.6-15.1 range.
    Manual truck for the record. 2003 S10 4.3 5 speed for those who dont know...
    When I put it in gear, give some gas, let clutch out and start to move, it goes way lean to 17s!! Like I guess its called tip-in?
    Why would it do that all of a sudden?

    I do notice that also my base timing in neutral and in gear are different than my stock orig tune. But thats all I see different other than slight 2* + adv on Hi and Lo spark tables, the afformentioned afr/pe ratio adjustments and my reg tire/gear/dfco speed/shiftlight/etc fixes I wanted. But those have been done for long time.

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    I can take a log real fast of it doing this. Just need to know what pids to log for best viewing

  4. #4
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    No one? I finally threw a PO171 and PO174 codes this weekend. I was out and didnt have laptop to log or read codes until this morning. I work shifts of 10hrs from 6am to 4:30, so after work was my first log run. I attached it.

    I decided to reflash the PCM with a prior tune that was simply my gear/tire corrections, speedo cutoff limit raised, shiftlight removal, PO420 code removal, etc. A tune I ran for a long time with no issues.
    Just like the other day, I reflashed the PCM no problem. But first restart after flash the AFR wideband gauge reads over at 17.x:1 super lean. At idle. Stays there until I rev it and even then its not instant that it comes off. Now the truck is up to operating temps indefinately.
    Same thing it did the other day.
    DFCO works as normal after 25mph, when I am cruising, let off, then after needs are met, then DFCO kicks on...and unless I drop below 25 (set MPH of this to activate), or tip the throttle back on. I have manual so I get that fuel cut off (like DFCO) in between shifts. IDK where to adjust that from however and thats not a prob.
    But If I am coming from a cruise to a redlight, disengage DFCO (if its active at the time) by going to neutral and coasting to the light, I get the 17.X:1 AFR super lean problem. Has never done this before :( IDK why its doing it now.
    I only changed the Commanded AFR from 14.2:1 to 14.4:1 since I felt the E10 (up to 10%) was a bit weak on the E.

    Someone have insight??

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    Log and file
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