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2G Rpm drop with AC on

Posted by NFSPD_FL, Mar 25, 2020

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    NFSPD_FL Probationary Member

    Joined Feb 16, 2020
    Melboune, Florida
    I have read several threads about RPM drop and tried some of the suggested fixes but my issue remains. I would like to see if anyone out there had this issue and what the fix was.

    My RPMS drop and almost stall the car when the AC is turned on and will return to normal if I turn AC off. Everything pointed to the Idle Air Control Valve. So I replaced it with a new Standard motor products one model AC146. But it still does the same exact thing. I have ECM link and my throttle position shows good.

    Any help or suggestions will be appreciated.

    140  1

    1998 Eagle Talon TSi AWD
    manual · 2G DSM
  2. gofer

    gofer Moderator

    Joined Feb 18, 2006
    South Gilbert, Arizona
    ...activate your IdleAir tables in ECMLink and see if it has any positive effect.

    Street Build 18K  13  61

    1997 Mitsubishi Eclipse GST
    11.634 @ 126.050 · 2G DSM

    3K  0

    1997 Mitsubishi Eclipse N/T
    manual · 2G DSM
  3. luv2rallye

    luv2rallye DSM Wiseman

    Joined Jun 7, 2003
    Minneapolis, Minnesota
    Are you using the stock 4 wire connector factory alternator? The stock factory 2g has an alternator connector with 4 wires instead of some 2 wire aftermarket (or the 1g's 2 wires). One of the extra wires (green wire - "FR signal") is an internal alt load sense line signal to the ECU (pin 41) which controls idle speed (IAC) when extra load is present on the alt (like AC or high beams with blower and WOT). I don't know how/if ECMLink handles this. On my stock 99 the rpm actually increases when I turn on the AC due to this signal.
    Last edited: Mar 26, 2020

    3K  0

    1999 Mitsubishi Eclipse GST
    14.200 @ 95.000 · 2G DSM
  4. motomattx

    motomattx Proven Member

    Joined Dec 9, 2010
    wampum, Pennsylvania
    Are you sure that your air conditioner compressor is in good shape and has plenty of refrigerant and oil in it? its hard for me to believe that any Dsm a/c system still has the factory fill in it without having any refrigerant added over the years, and when its added it waters down what oil is in the system to the point where if enough refrigerant is added there will be little to no oil left in the system, this will wreck your compressor over time, so you might have a compressor that is locking up.

    Drag Race Build 4K  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
    TSiAWD666 likes this.

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