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99 mitsubishi eclipse 420a ecu issue

Posted by Big Viking, Sep 20, 2020

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  1. Big Viking

    Big Viking Probationary Member

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    comer, Georgia
    New member... long time reader. I have just rebuilt my 99 mitsubishi eclipse 420a. We have added a super 16g turbo, forged pistons and h beam rods. Stage 2 Brian crower cam (.409 lift). 370 cc injectors and a 12:1 fuel pressure regulator. Full 3 in straight exhaust. I'm beginning to think that the stock ecu is confused.... It runs but its not "happy". Thoughts, ideas and or products to help?
     
    609DSM likes this.
  2. dsmcrzy

    dsmcrzy Proven Member

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    You need a way to actually tune it (megasquirt). Does it run fine at idle? If it’s cutting out in boost it’s because the stock MAP sensor can’t read positive manifold pressure.
     

    Street Build 5K  13

    1996 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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    BLACK'98DSM likes this.
  3. Big Viking

    Big Viking Probationary Member

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    comer, Georgia
    It does seem to run fine as idle. Even revving the engine in park/neutral, but once its under a load... Its currently "missing" at around 2500-3000 rpm or any rpm that is held steady. The vacuum is lower than i think it should be, its around -10 to -12 in hg. I did lower compression from 9.8:1 which i believe is stock down to 8.5:1. It has a "missing link" for the map sensor. Im looking at the AF/X ecu or haltech 1000 elite... as a possible solutions. thoughts? Im not very good at wiring so I thought plug and play...
     

    Attached Files:

  4. dsmcrzy

    dsmcrzy Proven Member

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    The AF/X ecu won’t do anything for you now. That’s still limited to NA. As far as I know, there is no plug and play solution for the 420a. I know there were a couple companies looking at it years ago but it never made it because the market is small.

    do you have a wideband gauge? What’s that reading at idle, etc?

    The missing links are also hit and miss. Sometimes they work sometimes they don’t. What you really need is a fuel cut defender if you plan to keep the same setup you have now.
     

    Street Build 5K  13

    1996 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  5. BLACK'98DSM

    BLACK'98DSM Proven Member

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    IMO, anybody who plans to turbo their 420a needs to invest in a Megasquirt first. Even if they're just going to raise the compression and raise the cam duration... the stock ecu will still throw misfire codes... and it won't provide enough fuel. You can destroy very expensive setups because the stock ecu doesn't know how to handle them.

    Soon I'll be starting up my built 420a. It's going to be running an 11:1 compression ratio with 242 cams and a 60mm TB. There's no way the stock ecu is going to throw enough fuel at it. Sure, I bet it'll start and idle and rev... but at wot during a pull it'll be dangerously lean and break up causing an inconsistent pull.

    Long story short... get a tunable ecu. Megasquirt is the main option. Fuel cut defenders and SAFC's are a slightly cheaper option (sometimes) but that just depends on whether you'd like to spend your time and money on something that only controls your fuel management or the whole engine parameters (as displayed by the Chrysler sensors anyway).

    Edit: Hey are you running an MLS headgasket? You're supposed to resurface your block if so. I guess it's too late now but for future reference, they don't always seal if you skip that step
     

    Road Race Build 4K  10  25

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

    78  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
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  6. Big Viking

    Big Viking Probationary Member

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    comer, Georgia
    i dont have a wide band. i know i need one but i don't know anything about them. at idle the narrow band is reading .8 volts showing rich exhaust. i did upgrade the injectors to 310cc... i wanna go bigger, but i figure i should get it running first then increase again.
     
  7. Big Viking

    Big Viking Probationary Member

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    Joined Jun 25, 2020
    comer, Georgia
    Which MS should I run? I'm no good at wiring so i was hoping for a jumper plug of some sort or plug and play. My ecu is showing no codes, just kinda a miss fire at steady throttle. I am running a multi layer cosmetic head gasket. What can I do about the missing link? The map sensor goes crazy if it sees boost. My stock ecu ran my stock engine (before the build) with this turbo and 310cc injectors on 2 stage boost (5 and 10 psi). Im more of a mechanic than an electrician, and I'm not afraid to throw money at the build. this is just my first build and I wanna do it justice.
     

    Attached Files:

  8. dsmcrzy

    dsmcrzy Proven Member

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    There’s a problem right there. The ecu still believes the stock injectors are there. if you are running the same base fuel pressure you will be running rich. The only way to get that dialed in with that FMU setup and bigger injectors is to lower the base fuel pressure.

    as far as wide band gauges go... there’s not much to know. Power, ground and oxygen sensor in the downpipe.
     

    Street Build 5K  13

    1996 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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    BLACK'98DSM likes this.
  9. dsmcrzy

    dsmcrzy Proven Member

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    Did you have the 12:1 FMU in place on the stock engine? It was that added with the build?
     

    Street Build 5K  13

    1996 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  10. Big Viking

    Big Viking Probationary Member

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    Joined Jun 25, 2020
    comer, Georgia
    yes i have 12:1 fmu installed
     

    Attached Files:

  11. Big Viking

    Big Viking Probationary Member

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    Joined Jun 25, 2020
    comer, Georgia
    im running 310 cc injectors. im going to lower fuel pressure today. i was running at apx 35psi. probably go down to 20 psi and see how that works.
     
  12. Jays99Spyder

    Jays99Spyder Proven Member

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    I'm no expert at this but sounds like you need to know how it's running(lean or rich). You need a wide band they are super easy to do, this way you know whats going on. Then something to control your fuel, whether it be something with the ecu or a safc.
     

    Street Build 321  4

    1999 Mitsubishi Eclipse GS Spyder 4G63 Swap
    fwd · manual · 4G63t Swapped
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  13. Big Viking

    Big Viking Probationary Member

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    Joined Jun 25, 2020
    comer, Georgia
    ok, so i dropped the fuel pressure to 20 psi. took out the "Missing link". the vacuum came up to -16 psi. fuel air ratio is still swinging full rich to full lean at idle. Acting like its got a vacuum leak, rev up a little and then stumble rev up a little then stumble... took it out for a test drive, about 4,000 rpm with 3 psi boost it starts stumbling hard. wont go above this point. plugs are gapped at .028 and the are ngk type r bkr5e. in idle i can rev past 4,500 and no real problems noted... ideas?
     
  14. Jays99Spyder

    Jays99Spyder Proven Member

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    Those narrow af gauges are not accurate, need a wide band for a more true reading, also have you done a boost leak test? If not I highly recommend it.
     

    Street Build 321  4

    1999 Mitsubishi Eclipse GS Spyder 4G63 Swap
    fwd · manual · 4G63t Swapped
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  15. Big Viking

    Big Viking Probationary Member

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    comer, Georgia
    how do i perform a boost leak test? also the ignition timing is controled by the ecu and is all over the place...
     
  16. Jays99Spyder

    Jays99Spyder Proven Member

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    There are so many threads on here on how to build a boost leak tester and how to perform one. If you can't fined it on the search just type in Google search "2g dsm, then your question and it will bring you back to dsm tuners to related threads. Good luck
     

    Street Build 321  4

    1999 Mitsubishi Eclipse GS Spyder 4G63 Swap
    fwd · manual · 4G63t Swapped
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  17. Big Viking

    Big Viking Probationary Member

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    comer, Georgia
    why would a boost leak cause this?
     
  18. BLACK'98DSM

    BLACK'98DSM Proven Member

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    And it will remain that way.

    Here is a video of how the stock ecu handles cams... all it takes is cams to throw off the ignition timing.



    +1 on a WIDEBAND gauge.
     

    Road Race Build 4K  10  25

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

    78  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
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  19. Jays99Spyder

    Jays99Spyder Proven Member

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    Waukegan, Illinois
    Anytime you have forced induction you should perform a boost leak test to make sure there is no leaks, a leak will cause power loss. Check all sensors too a unplugged sensor can throw off the ecu.
     

    Street Build 321  4

    1999 Mitsubishi Eclipse GS Spyder 4G63 Swap
    fwd · manual · 4G63t Swapped
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    BLACK'98DSM likes this.
  20. Big Viking

    Big Viking Probationary Member

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    comer, Georgia
    ok, no vacuum leakes and leak down test shows all cyliders are closed.... so its on to ecu. preference?
     
  21. Jays99Spyder

    Jays99Spyder Proven Member

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    Waukegan, Illinois
    Boost is a little different then vac lines. Need to put positive pressure into the turbo and check for leaks. I would do at least 20psi
     

    Street Build 321  4

    1999 Mitsubishi Eclipse GS Spyder 4G63 Swap
    fwd · manual · 4G63t Swapped
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  22. Big Viking

    Big Viking Probationary Member

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    Joined Jun 25, 2020
    comer, Georgia
    ok, so no vacuum leaks. leak down test is all good. spark plugs are looking good. vacuum is still lower than i think it should be, but im willing to roll with it. -13 to -17. down to tuning..... any plug and play ecus out there? im no good at wiring. megasquirt, aem, haltech,af/x any others i should look at?
     
  23. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Most of those are no longer in production. No matter what you buy, you'll have to do a small amount of fab or wiring. I promise it's nothing you can't figure out if you take the time.
     

    Road Race Build 4K  10  25

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

    78  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
    Loading...
    Big Viking likes this.
  24. Big Viking

    Big Viking Probationary Member

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    Joined Jun 25, 2020
    comer, Georgia
    suggestions on the best on? least wiring most tunablity...
     
  25. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Joined Feb 9, 2019
    Hoover, Alabama
    Most tunability = Megasquirt. But it will definitely require wiring. Especially if you want to remove the stock ecu.
     

    Road Race Build 4K  10  25

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

    78  5

    1998 Ford Mustang GT
    rwd · manual · Misc Vehicles
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