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2G Weak spark on 2/3. Poor idle, spark blowout/washout above 4-5 psi

Posted by Tanro, Apr 15, 2018

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  1. Tanro

    Tanro Proven Member

    1,469
    68
    Joined Jul 22, 2009
    Montgomery, Alabama
    I've got a very weak spark on 2/3 and any amount of load will cause the car to bog down and misfire like crazy. Doesn't matter if its boost, or just 4th / 5th gear if you try and give it more than 1/4 throttle or it gets above 4-5 psi it just starts missfiring terribly.

    New parts include:
    TPS <- Adjusted per 2g service manual
    ISC
    Both Coils. Doesn't matter if you swap them the weak spark stays on 2/3.
    Coil pack wiring has been rewired with 14awg
    Igniter (PTU)
    Mass Airflow
    Coolant Temp Sensor
    Battery
    Alternator
    0GA Wire from alternator to fusebox.

    I've been trying to diagnose this for a year now with no luck. It gets better and it gets worse, but never goes the f*** away.

    If you pull the spark plug wires they won't arc to the valve cover/head on 2 or 3. If you use a spark checker it barely lights up as compared to to glowing bright red with 1/4.

    I even tried swapping the wires on the harness side (harness to ecm) and then the plug wires as well to see if the weak spark moved to 1/4 but it seemed to make the engine run like total garbage. However it did improve the spark on 2/3 but did not make 1/4 worse.

    The car is throwing the infamous p0300 code, buts a 2gb engine, with 2gb sensors, in a 2gb shell, with 98/99 h8 ecu. I am ready to get this stolen and file an insurance claim at this point. A 420a car would be faster than this pile of junk and new parts.

    What can I possibly do to get a stronger spark?
     

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    Last edited: Apr 15, 2018
    My DSM:
    1999 Mitsubishi Eclipse GST

    Street Build

    16g   manual
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  2. shinzon

    shinzon Proven Member

    234
    38
    Joined Sep 11, 2006
    St. Petersburg, Florida
    How are your grounds? What kind of voltage are you reading at pin 3 (black with white) on the Coil? How about pin 6 (black with white) on the PTU? What are you reading on pin 1 (green with yellow) on the TPS?
     
    Last edited: Apr 15, 2018
    My DSM:
    1996 Eagle Talon TSi AWD

    14b   automatic
    1997 Eagle Talon TSi AWD

    T25   automatic
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  3. Tanro

    Tanro Proven Member

    1,469
    68
    Joined Jul 22, 2009
    Montgomery, Alabama
    Will get you some voltage values. You want them with Key on Engine off, or Key on engine running?

    Grounds are fine, I've cleaned them, they are tight, had added some extra ground cables with no help.
     
    My DSM:
    1999 Mitsubishi Eclipse GST

    Street Build

    16g   manual
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  4. shinzon

    shinzon Proven Member

    234
    38
    Joined Sep 11, 2006
    St. Petersburg, Florida
    Key on engine off should be fine.

    Have you checked ground by the ECU (ground 10 in the manual)? Have you checked ground 3, the one in the engine bay on the firewall by the cruise control module? PTU grounds on #3.

    edit: could you also give me a couple of pictures of your engine bay? Maybe a wide shot of the whole thing, and a close up on the intake manifold, coil area. Just want to see what I'm working with.
     
    Last edited: Apr 15, 2018
    My DSM:
    1996 Eagle Talon TSi AWD

    14b   automatic
    1997 Eagle Talon TSi AWD

    T25   automatic
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  5. Tanro

    Tanro Proven Member

    1,469
    68
    Joined Jul 22, 2009
    Montgomery, Alabama
    Yeah I will take some pictures tomorrow while I am getting voltages for you.

    I don't have cruise. I have the ground strap from the IM to the firewall. The ground lug next to the passthrough for the wiper motor. Ground lug for the fusebox harness next to the a/c accumulator. Ground lug inside under the dash. Ground cable from the transbellhousing to the battery, and a ground cable from the battery to the firewall.
     
    My DSM:
    1999 Mitsubishi Eclipse GST

    Street Build

    16g   manual
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  6. Tanro

    Tanro Proven Member

    1,469
    68
    Joined Jul 22, 2009
    Montgomery, Alabama
    Fixed it by cutting out all the stock wiring and redoing it. (PTU and Coils) Spark is still week at idle, but for the first time in a year this thing doesnt have blow out under load.
     
    My DSM:
    1999 Mitsubishi Eclipse GST

    Street Build

    16g   manual
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    Dsm panda and shinzon like this.
  7. luv2rallye

    luv2rallye DSM Wiseman

    7,338
    448
    Joined Jun 7, 2003
    Minneapolis, Minnesota
    The back side of the PTU is also a ground which is much better (handles more current) than it's pin 3. PTU needs to be in it's mounting bracket and bolted to engine. The back side/bracket is also is used to dissipate PTU heat so it needs to be there. Also make sure the battery large negative cable goes under a starter mounting bolt (as well as a separate cable to body) so engine is well grounded.
     
    My DSM:
    1999 Mitsubishi Eclipse GST

    14.200 @ 95.000 MPH
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