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Thread: STFT at idle kicking my butt

  1. #1

    STFT at idle kicking my butt

    I've been running around tuning both on the street as well as some dyno time lately. I've been tuning in open look to get MAF tables and all that dialed in where they should be. I'm .98-1.02 lambda at idle per the wideband controller in open loop. When I re-enable closed loop, my short term fuel trims are -17% for bank 1 and -7% bank 2 at idle pretty consistently. My wideband is in bank 2. Do I need to add a negative voltage offset in the B1 and B2 sensors to get this to align better? I've had this problem for as long as I've been tuning with a wideband. Something has to be wrong. I've swapped the O2 sensors side to side and also replaced them with new ones within the last year. I'm running E85 and have stoic set to 9.8 in the tune.

    2007 Mustang GT listed in my signature.
    2007 Mustang GT
    305ci big bore (5.0L Cammer block)
    Ported heads
    Lunati cams and springs
    Usual compliment of bolt-ons

  2. #2
    Advanced Tuner
    Join Date
    Sep 2010
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    872
    Quote Originally Posted by csracing View Post
    I've been running around tuning both on the street as well as some dyno time lately. I've been tuning in open look to get MAF tables and all that dialed in where they should be. I'm .98-1.02 lambda at idle per the wideband controller in open loop. When I re-enable closed loop, my short term fuel trims are -17% for bank 1 and -7% bank 2 at idle pretty consistently. My wideband is in bank 2. Do I need to add a negative voltage offset in the B1 and B2 sensors to get this to align better? I've had this problem for as long as I've been tuning with a wideband. Something has to be wrong. I've swapped the O2 sensors side to side and also replaced them with new ones within the last year. I'm running E85 and have stoic set to 9.8 in the tune.

    2007 Mustang GT listed in my signature.
    What are your times while driving? Idle trims could be skewed depending on MAF placement and how straight the air is when it hits the MAF. also do you test your e85 to make sure you are actually getting e85?

  3. #3
    Haven't looked at trims while driving yet as all of my time to this point has been in open loop. I had this exact same problem on 93 octane so it's not a fuel problem.
    2007 Mustang GT
    305ci big bore (5.0L Cammer block)
    Ported heads
    Lunati cams and springs
    Usual compliment of bolt-ons