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  • Ms & a/c

    So my car was running rich and had a high idle and I finally addressed it last weekend. So it idles better and at sits in the high 14's (air fuel wise).

    But now, with the a/c on, when you come off the throttle the car dies because the rpm's drop too much. But before I smoothed everything out the a/c and ms played nice with each other.

    Is there a setting that prevents the rpm's from going below a certain point in this case, that would help me with the car dying because of the rpm's dropping too much when the a/c is on? If so what is that setting called?

    Or do I need to raise the rpm's in the fuel table where it sits when the a/c is on?

    Or is there another method I don't know about?
    '94 Red PGT Gone, but Project PGT has begun
    '04 Black SRT-4 Um, no it's not stock. But "It's just a Neon, right?" 379whp @ 20lbs *Sold*

  • #2
    Which Megasquirt do you have?
    There is a "Air Conditioning Idle-up" menu in TunerStudio. You need to wire a input into MS to let it know the A/C is being commanded on. I've never used it but it may be worth looking into.
    '94 Probe Originally 2.0L, MTX - Now KL-DE 2.5L, MTX
    KL-ZE Intake manifold, Custom 3" intake w/ velocity stack, OBX headers, Mandrel Exhausts Systems 2.25" w/ 18" resonator and Borla muffler
    Megasquirt 2, Wasted spark

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    • #3
      MS2 v3.0

      No ideas what "code" its running though.
      '94 Red PGT Gone, but Project PGT has begun
      '04 Black SRT-4 Um, no it's not stock. But "It's just a Neon, right?" 379whp @ 20lbs *Sold*

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      • #4
        also having this issue...

        Greg 94 PGT,

        Funny you mention this. I am trying to figure out the same issue with my almost "stock" 95 Probe GT running DIYPNP on MS2/extra 3.4.2 code with all hardware and jumper wires setup as per instructions on the DIYAutotune instructions.

        Anytime the AC is engaged during idling, the RPMs fall way too low. During regular cruising, its not an issue at all. I'll continue plugging away at this issue this week.

        1995 Ford Probe GT, black - Garrett GT3076-R @ 11.2psi. ~321ish whp/303ish wtq @ 19-20○ ignition, DIYPNP MS2/extra, etc. -parted & junked
        1995 Ford Probe GT, black - MS3-Pro Ultimate, bone stock-ish, daily driver)

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        • #5
          Thanks.

          I haven't played with it since I noticed. I wasn't sure if there was a solution somebody was already aware of.

          And since I smoothed out the idle I figured I would check with PT before experimenting.
          '94 Red PGT Gone, but Project PGT has begun
          '04 Black SRT-4 Um, no it's not stock. But "It's just a Neon, right?" 379whp @ 20lbs *Sold*

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          • #6
            Actually, somewhat got it running pretty decently during idle now. The thing is, you have to run Idle in Closed-Loop mode. Takes a TON of finessing but I think I got it somewhat decent.

            Whenever I'm idling, and turn on the A/C, the load (kpa in MAP) increase, so it takes the MS a few seconds to increase the RPM. I'm still tinkering with the P.I.D. settings to get it just right. The issue so far, has been when I decide to turn off the A/C, the RPMs still continue to stay up sometimes. Not always.
            1995 Ford Probe GT, black - Garrett GT3076-R @ 11.2psi. ~321ish whp/303ish wtq @ 19-20○ ignition, DIYPNP MS2/extra, etc. -parted & junked
            1995 Ford Probe GT, black - MS3-Pro Ultimate, bone stock-ish, daily driver)

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            • #7
              How did you guys keep the AC
              1996 Boysenberry Probe GT MTXtreme
              2014 Fusion SE MTXtreme
              2005 Mountaineer Premier

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              • #8
                Originally posted by spada View Post
                How did you guys keep the AC
                Jordan initially tuned my MS, so I don't know if he set it up specifically or not for a/c.

                But I figured out my issued above was from me not having the MS in Closed Loop. Once I switched it back to Closed Loop it stopped dropping the rpms too much when letting off the throttle.
                '94 Red PGT Gone, but Project PGT has begun
                '04 Black SRT-4 Um, no it's not stock. But "It's just a Neon, right?" 379whp @ 20lbs *Sold*

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                • #9
                  yeah, I always run closed loop idle, it works well once the fans kick on.

                  But I'm not so concerned about having the idle work correctly, I just want to know how to keep the A/C working. I assume I can simply jump the A/C wires together..... but which ones?
                  http://www.pazzer.net/pazzer/served/...2.5GT/C246.GIF
                  1996 Boysenberry Probe GT MTXtreme
                  2014 Fusion SE MTXtreme
                  2005 Mountaineer Premier

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                  • #10
                    The MS2/Extra code has an A/C idle up function in 3.3.0 and later. You'd need an on/off input to activate this, and when you do that it will automatically open the IAC valve more when the A/C turns on.
                    Matt at DIYAutoTune.com
                    My PM box fills up fast - it's much better to email me at websales@diyautotune.com

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                    • #11
                      I'm not worried about idle, i just want to know if i can keep air conditioning, and how.
                      1996 Boysenberry Probe GT MTXtreme
                      2014 Fusion SE MTXtreme
                      2005 Mountaineer Premier

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                      • #12
                        @spada, absolutely, bro! Been like that for me since I transferred my DIYPNP from my non-AC boosted PGT to my daily driver. Currently rocking my MS3-Pro Ultimate and as soon as this engine goes inside the car, I'm going to tinker with perfecting the AC/idle up settings along with the sequential fuel and spark (courtesy of the KLG4 cam position sensor).

                        I'll keep y'all posted.

                        Dan
                        1995 Ford Probe GT, black - Garrett GT3076-R @ 11.2psi. ~321ish whp/303ish wtq @ 19-20○ ignition, DIYPNP MS2/extra, etc. -parted & junked
                        1995 Ford Probe GT, black - MS3-Pro Ultimate, bone stock-ish, daily driver)

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