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420A High Idle Issue

Posted by RJ_IS_BATMAN, Jul 9, 2020

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  1. RJ_IS_BATMAN

    RJ_IS_BATMAN Proven Member

    52
    5
    Joined May 7, 2020
    Ontario, California
    Hey Everyone,

    Ive been having an issue where my idle stays around 1.5k and if i turn the ac one it will want to die out for a second then go up to 1.5 and the idle will go up and down. Where should i start to try to find the source of the issue?

    Heres some info on my car
    420A with a cold air intake, aftermarket headers and the previous owner had the car straight piped.

    Should i start by replacing the coil, plug wires and spark plugs? The car sat for about a year without driving due to the previous owner breaking the shift linkage cables.
     

    Street Build 253  22

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  2. DevineAstral

    DevineAstral Proven Member

    72
    21
    Joined Jan 1, 2020
    Irvona, Pennsylvania
    i recommend troubleshooting before replacing any of the ignition components. It could any number of things. could be idle air control, MAP sensor, possibly the ignition but the engine should run low and and try to stall constantly, not run high. Might also be a vacuum leak or issue somewhere. is it throwing any codes or anything? and it only tries to stall out when the AC is on? or is it just random whether AC is on or off?
     

    Street Build 147  3

    1996 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    Street Build 227  3

    1997 Mitsubishi Eclipse Spyder GST
    fwd · manual · 2G DSM
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  3. RJ_IS_BATMAN

    RJ_IS_BATMAN Proven Member

    52
    5
    Joined May 7, 2020
    Ontario, California
    Yeah, its weird because for a while it was at around 1k for idle and would only jump up to 1.5k with the ac turned on and thats where it would try to stall out and go up and down between .5k and 1.5k to stay on while the ac was running. No check engine light at all, just the higher then normal idle.

    When i got the car a lot of the engine was disassembled so im not sure if there's a vacuum leak due to a missing gasket somewhere possibly.
     
    Last edited: Jul 10, 2020

    Street Build 253  22

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
    Loading...
  4. DevineAstral

    DevineAstral Proven Member

    72
    21
    Joined Jan 1, 2020
    Irvona, Pennsylvania
    in that case, check your vacuum lines, check the gaskets around the throttle body and/or intake. then your idle air control. idle speed sensor. MAP sensor. i'm no gurus like most of the people on here but i'm almost certain that your problem lays within one of those things.
     

    Street Build 147  3

    1996 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    Street Build 227  3

    1997 Mitsubishi Eclipse Spyder GST
    fwd · manual · 2G DSM
    Loading...
  5. RJ_IS_BATMAN

    RJ_IS_BATMAN Proven Member

    52
    5
    Joined May 7, 2020
    Ontario, California
    Ok so...Took the time today to take apart some of the bolt ons and found the issue, The egr tube was only hand tightened and i think thats where my issue was, i tightened it up and the car idled around 1k even with the AC on full blast. Drove the car around and no stalling what so ever and thats with the temperature at about 100-102 today in Cali. No overheating either.
     

    Street Build 253  22

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
    Loading...
    DevineAstral likes this.
  6. DevineAstral

    DevineAstral Proven Member

    72
    21
    Joined Jan 1, 2020
    Irvona, Pennsylvania
    Glad to hear that you got it sorted out! I completely forgot about the EGR being a possibility.:ohdamn:.Probably because the last time i had an issue with mine was in the single digits during winter and the my car kept trying to stall out. I forgot it could work the other way around too. glad to hear you're up and running fine with no more issues!
     

    Street Build 147  3

    1996 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    Street Build 227  3

    1997 Mitsubishi Eclipse Spyder GST
    fwd · manual · 2G DSM
    Loading...

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