Car Dying with A/C

Discussion in 'ecu-GN Tech Help' started by wiseman, Jul 18, 2019.

  1. wiseman

    wiseman Active Member

    Hi Eric,
    I recently went from a TT 6.1 chip to the ECU GN. The car runs fine until the A/C compressor is turned on and I press the gas . Once I press the gas or tap it (with the A/C on), the car boogs down then dies immediately after the gas is released. It does it constantly and consistently every time.

    I have included a log where I have turned the A/C on a number of times and it has died every time back to back. Do you have any ideas from the attached log of any adjustments that may need to made?

    Note: There were no issues with the A/C compressor and the car dying with my old 6.1 chip.

    P.S. I tried to send the log, but looks like I cant upload an .msl file. I can email it to you if you like.
  2. EricM

    EricM Administrator Staff Member

    I changed the accepted files to add msl and msq, so you should be able to add it now.

    What ignition system are you using, stock or something else?
  3. wiseman

    wiseman Active Member

    I am running a stock ignition system.

    I have attached my log.

    Attached Files:

  4. EricM

    EricM Administrator Staff Member

    Ok, I see what might be happening. It appears to be IAC related.

    First, I would adjust your throttle stop to bring the IAC number down. Right now it looks like, in park, warmed up, you are at around 55 for IAC (a/c off). I would open the throttle blade maybe 1/2 turn (clockwise), then recalibrate the TPS in the software. Try to get it down around 20-30.

    Then, if that doesn't fix it, we'll need to adjust the "closed loop idle initial values" table. That dictates what the IAC does when you let off the throttle. Right now, in your log, the IAC is around 99 or so with the A/C on, then when you blip the throttle, it's commanded to go lower, around 80, which can make it stall.
  5. wiseman

    wiseman Active Member

    ok thanks. I will make the adjustments tomorrow and report back the results.
  6. wiseman

    wiseman Active Member

    Hi Eric,
    I just finished making the adjustments as you mentioned above.

    I 1st adjusted the IAC to around 20-22, and it idled much better with the A/C running (it still stumbled a bit, but it didnt die). I then adjusted the IAC down a bit further to around 15-16 and the car did even better. The stumble was not nearly as bad after the 20-22 setting and the car didnt die (but it still is a bit noticeable).

    Note: I have noticed the with the A/C on after I let of the gas, the car will go extremely lean (like 19.9), Then it will recover shortly after to the targeted AFR. Is this normal?

    I have attached a short log, showing what it reacted with the IAC setting of 15-16

    Attached Files:

  7. EricM

    EricM Administrator Staff Member

    It looks like you'll need to work on the VE table a bit.
    First, at idle, I see your fuel correction is around 107-109%, so the ECU is adding about 9% to reach your target AFR. Find that area in the VE table by watching the bubble, and scale it up 9% (multiply by 1.09).
    You can do it live while idling.
    You want to get the correction closer to 100%, or even a tad lower, maybe 97-98%. It will float around a bit, but that's ok.

    I would start there and see how it affects the lean spot. We might have to adjust another area of the VE table also.
  8. EricM

    EricM Administrator Staff Member

    Another thing that helps fine tune the IAC when the A/C is on is the "idle up steps". This number is added on to the IAC when the A/C comes on, and also when you let off the gas.

    For example, if your IAC is around 25 idling with the A/C off, but it climbs to 55 with the A/C on, then you could set the idle-up steps to 30, so it will add it right away when the A/C comes on.


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