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Discuss Jeep with GM TBI swap in the alt.autos.gm forum at Car Dealer Forums; Hey Guys, I'm sure this isn't one you will come across often. I've put a ...
  1. #1
    grockswo
    Guest

    Default Jeep with GM TBI swap

    Hey Guys,
    I'm sure this isn't one you will come across often. I've put a Howell
    TBI kit onto my Jeep (AMC) 304 V8. It's got hedders, glass packs, and
    an Edelbrock Performer intake. I have an adapter to mate the GM TBI to
    the intake. And it uses the GM ECM and a Howell-made wiring harness.
    Some of the wiring colors don't match up to GM wiring colors. But I
    have the kit installed and wired up, and the fuel pump and lines all on
    it, it runs, but it runs too rich at idle prior to closed-loop
    operation. Once it goes closed loop and runs fine. Gets a bit too
    much fuel when really goosing it, but I've backed off the fuel pressure
    regulator about as much as possible. I've cleaned out the TB, the IAC
    port, etc, and it still doesn't want to idle properly, it's trying to
    idle at 600 rpm, with some surging, to about 700 rpm. But as it
    continues to run rich at idle it will foul a plug and eventually stall
    the engine. I have adjusted the TPS setting so it is at 0.6V with the
    throttle plate fully closed as per the manual. When I first tried that
    it would start, but wouldn't stay idled, it would stall out. So I
    increased the setting on the TPS until it would actually idle. It's
    now set at 0.75V with the throttle plate closed. And it ran fine for a
    little while, but would eventually idle down from about 850-900 all the
    way down to approximately 400-550 with a good bit of surging as the IAC
    <I assume> was trying to regulate the idle. I have checked the IAC, it
    measures out fine as far as Ohming it out, the MAP sensor reads good as
    well. And the TPS works just fine as well. I don't have the ESC set
    up on mine, it's running with a stock Jeep distributor, ignition module
    and an Accel super coil. Does anyone have any ideas on what might be
    causing the trouble and how to fix it. Also, when it is idling, I
    think with my current exhaust set up and the location of the o2 sensor,
    it's not getting hot enough to stay closed loop at idle speeds. I have
    it mounted just past the collector on the hedders, but since there is
    no cat (it's a 1973 Jeep), I'm guessing it's not staying hot enough,
    should I look into a 3 wire o2 sensor, right now it's a regular one
    wire set up. The TBI system is the same as the 86-90 truck set ups.
    As far as I know, it's the TB system for a chevy 350. I'm at a loss,
    about ready to make a bypass for the o2 sensor for when it's at idle
    and force it to run closed loop even if the o2 sensor isn't hot enough,
    just substitute the voltage output it should be sending to the ECM.
    I've been trying for quite a while to get it going right, without much
    luck. Also, it's a manual transmission, I've seen there are two
    different version PROMs one for an auto and one for a manual, could
    this be causing problems as well, I'm not certain which one I have,
    didn't bother to open up the case and see what number is on it.

    Gus




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  2. #2
    Jarhead
    Guest

    Default Re: Jeep with GM TBI swap


    "grockswo" <grockswo@vt.edu> wrote in message
    news:1153935415.888702.223920@m79g2000cwm.googlegr oups.com...
    | Hey Guys,
    | I'm sure this isn't one you will come across often. I've put a Howell
    | TBI kit onto my Jeep (AMC) 304 V8. It's got hedders, glass packs, and
    | an Edelbrock Performer intake. I have an adapter to mate the GM TBI
    to
    | the intake. And it uses the GM ECM and a Howell-made wiring harness.
    | Some of the wiring colors don't match up to GM wiring colors. But I
    | have the kit installed and wired up, and the fuel pump and lines all
    on
    | it, it runs, but it runs too rich at idle prior to closed-loop
    | operation. Once it goes closed loop and runs fine. Gets a bit too
    | much fuel when really goosing it, but I've backed off the fuel
    pressure
    | regulator about as much as possible. I've cleaned out the TB, the IAC
    | port, etc, and it still doesn't want to idle properly, it's trying to
    | idle at 600 rpm, with some surging, to about 700 rpm. But as it
    | continues to run rich at idle it will foul a plug and eventually stall
    | the engine. I have adjusted the TPS setting so it is at 0.6V with the
    | throttle plate fully closed as per the manual. When I first tried
    that
    | it would start, but wouldn't stay idled, it would stall out. So I
    | increased the setting on the TPS until it would actually idle. It's
    | now set at 0.75V with the throttle plate closed. And it ran fine for
    a
    | little while, but would eventually idle down from about 850-900 all
    the
    | way down to approximately 400-550 with a good bit of surging as the
    IAC
    | <I assume> was trying to regulate the idle. I have checked the IAC,
    it
    | measures out fine as far as Ohming it out, the MAP sensor reads good
    as
    | well. And the TPS works just fine as well. I don't have the ESC set
    | up on mine, it's running with a stock Jeep distributor, ignition
    module
    | and an Accel super coil. Does anyone have any ideas on what might be
    | causing the trouble and how to fix it. Also, when it is idling, I
    | think with my current exhaust set up and the location of the o2
    sensor,
    | it's not getting hot enough to stay closed loop at idle speeds. I
    have
    | it mounted just past the collector on the hedders, but since there is
    | no cat (it's a 1973 Jeep), I'm guessing it's not staying hot enough,
    | should I look into a 3 wire o2 sensor, right now it's a regular one
    | wire set up. The TBI system is the same as the 86-90 truck set ups.
    | As far as I know, it's the TB system for a chevy 350. I'm at a loss,
    | about ready to make a bypass for the o2 sensor for when it's at idle
    | and force it to run closed loop even if the o2 sensor isn't hot
    enough,
    | just substitute the voltage output it should be sending to the ECM.
    | I've been trying for quite a while to get it going right, without much
    | luck. Also, it's a manual transmission, I've seen there are two
    | different version PROMs one for an auto and one for a manual, could
    | this be causing problems as well, I'm not certain which one I have,
    | didn't bother to open up the case and see what number is on it.
    |
    | Gus
    |

    Do you think the TBI for the 4.3 V6 might make a difference? It is
    closer to the C.I. than the 350.

    --
    Jarhead




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  3. #3
    grockswo
    Guest

    Default Re: Jeep with GM TBI swap


    Jarhead wrote:
    > Do you think the TBI for the 4.3 V6 might make a difference? It is
    > closer to the C.I. than the 350.
    >
    > --
    > Jarhead



    I was actually looking, and according to what's on the Howell website
    and what it says on the tag that's attached to my TB, it's for a 4.3
    set up, either way they are all 500 cfm for those style of TBI set ups.
    So, I don't think that would be the problem either way. But that was
    something I had wondered about. But I checked for codes and there
    aren't any trouble codes stored in it. So my search continues. Thanks
    for the replies.

    Gus


  4. #4
    grockswo
    Guest

    Default Re: Jeep with GM TBI swap

    Well I went to the junkyard today and pulled a 3 wire o2 sensor from
    and 90 something buick Regal. Gonna try and wire that in, and
    hopefully with the heater built into it, it may work better. Will let
    you guys know, I'm headed out of town for the weekend so it won't be
    until Tuesday or Wednesday.

    Gus


  5. #5
    grockswo
    Guest

    Default Re: Jeep with GM TBI swap




    So I installed and wired up the heated o2 sensor (3 wire), it was still
    running rich on start up, but once warmed up it stayed closed loop
    during idle, so I think this will be a better set up. Taking it out
    tomorrow for a test run, will post more.

    Gus


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