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Thread: chevy tbi need help

  1. #1
    Carb and Points!
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    May 2020
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    chevy tbi need help

    hi i have few question and was hoping for advice/help

    i got an old 60's chevy truck and someone swapped a tbi engine in it .

    truck does not go over 50mph...no power. it feels good around the block but not on freeway....pedal on the floor and it feel like i dont go faster than the tembleweed
    truck always start the first time
    it idle good.cold around 1300 rpm warm arond 900 rpm
    when i drove it around the block and got it warm it would stall at a stop sign / red light/on gears . but not in park
    no back fire at all
    spark plug look good may a lit bit on lean side...but just a bit
    did a compression test and its fine
    fuel pressure 12 psi
    vacum gage 21
    tps is good
    injector are good
    new fuel filter
    gas tank clean
    throttle body super clen
    i checked the timing , timing is a 0 with the advance wire unplug ( i find out the timing light flash was not consistent ...sometime i can see a dead spot...not constant.. i tried different wires ans swap spark plug its still does it and not matter what cylinders i have the timing light connect to )

    wiring was a little jack up but was able to rewiring the obd connector to get the code out.
    here the code and here the real trouble .

    #31??
    #32
    #32
    #34
    #41
    #43
    #52
    #54
    #55

    ecm
    SERV NO 1227747
    86 ANLW K391031991

    i cleared the code... scanned it again .. find less codes but newer ones like #25 #35... turn off the keys..clear code again..
    grounded ( A12)ecm directly to battery , scanned again
    and all the first 9 codes came back


    before i start to chase ghost and stuff........
    do you guys think it could be a faulty ecm ?

  2. #2
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268
    Fuel ... Air ... Spark something is not right. Let's venture into Spark. I'm wondering if the TBI engine is using the FACTORY TBI EXTERNALLY MOUNTED IGNITION COIL?

    https://chevythunder.com/HEI%20remot...esting%201.jpg The chevythunder pic shows how to test the FACTORY TBI EXTERNALLY MOUNTED IGNITION COIL

    Sometimes pickups built in the 60's used a resistor wire for the points ignition coil. Sometimes the resistor wire is reused to power the FACTORY TBI EXTERNALLY MOUNTED IGNITION COIL. The FACTORY TBI EXTERNALLY MOUNTED IGNITION COIL uses a 12 AWG power wire from the ignition switch to the coil, WITHOUT a ballast resistor or WITHOUT resistor wire. What is the voltage on the TBI externally mounted coil when the engine is idling?

    dave w

  3. #3
    Carb and Points!
    Join Date
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    Quote Originally Posted by dave w View Post
    Fuel ... Air ... Spark something is not right. Let's venture into Spark. I'm wondering if the TBI engine is using the FACTORY TBI EXTERNALLY MOUNTED IGNITION COIL?

    https://chevythunder.com/HEI%20remot...esting%201.jpg The chevythunder pic shows how to test the FACTORY TBI EXTERNALLY MOUNTED IGNITION COIL

    Sometimes pickups built in the 60's used a resistor wire for the points ignition coil. Sometimes the resistor wire is reused to power the FACTORY TBI EXTERNALLY MOUNTED IGNITION COIL. The FACTORY TBI EXTERNALLY MOUNTED IGNITION COIL uses a 12 AWG power wire from the ignition switch to the coil, WITHOUT a ballast resistor or WITHOUT resistor wire. What is the voltage on the TBI externally mounted coil when the engine is idling?

    dave w
    thanks for your reply

    yes i do have a factory externally ignition coil
    i tested it and kept that on paper
    test1 : 00.5
    test2 : 1100
    test3 :i think nothing was showing i would have to test it again
    test4 :00.6

    about testing the voltage of the coil with engine idling... i dont know how to do it...im researching about that

    i will have to look for that ballastor resistor but i doubt .but i will look deeply
    i cant tell the person that swap the engine used the complete wiring harness from the donor truck ..complet engine harness , complete fuse boxe with harness for light and also the truck donor column steering...i only see new wires

    i was curious and open the ecm , and saw a jet perfomance chip....( i dont know if that matter ?)
    while engine idling with a multimeter at 20v , i get 0.02 volt on the ecm case??? is that normal ? ecm case doesnt touch the body or anything metallic

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