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Thread: 408 with 90/90 wont start

  1. #1
    Lifetime Member minytrker's Avatar
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    Default 408 with 90/90 wont start

    I have a 408 with a fast 90/90 setup and a good size cam. I can't get the car to start without giving it gas. I can't get it to idle either. I have tuned 402's before and never had a problem. The IAC is really high on also. I have added to the ve from 1200 on down,I have tried subtracting from the ve with no luck. Im lost.

  2. #2
    Lifetime Member Rhino79's Avatar
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    Try setting B4604 to something similar to:
    275.000000
    275.000000
    275.000000
    275.000000
    240.039063
    205.078125
    175.000000
    150.000000
    150.000000
    150.000000

    Between that, and desired airflow, that should get it starting pretty good, at least it worked for me on the last 408 I did which had a Victor Jr. and Edelbrock 4bbl.TB.

  3. #3
    Lifetime Member minytrker's Avatar
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    That helped some. The IAC is at 175 at around 1000 rpm. There is something also weird going on with the TPS. I can move the gas pedal a petty good ways before it the tps changes. It seems slow to respond. I have messed with the idle screw also.
    Last edited by minytrker; March 12th, 2007 at 11:03 AM.

  4. #4
    Lifetime Member oztracktuning's Avatar
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    Maybe reset your TPS sensor for a start. Disconnect it and key on (dont start the car) and then wait and reconnect it. This might help the slow to respond issue.
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  5. #5
    Lifetime Member minytrker's Avatar
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    Found one problem, bad tps. Just put a new one on will mess with it tommorrow. Being the 90TB blade has been messed with so much, by the owner and then by me can I set the new one up to factory specs by voltage? I dont have it in front of me, but isnt it supposed to read live .55 volts or something at 0% throttle?

  6. #6
    Lifetime Member Bruce Melton's Avatar
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    This does't have a LS2 cam sensor does it?

  7. #7
    Lifetime Member minytrker's Avatar
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    Quote Originally Posted by Bruce Melton
    This does't have a LS2 cam sensor does it?
    Not that I know of, but I will check tonight, Im 99% sure its ls1.

  8. #8
    Lifetime Member Bruce Melton's Avatar
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    It makes sense that it is LS1 but the way it is running is similar to the common reversed cam sensor lead on LS2s.

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  9. #9
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    If the iac is at 170 then open the TB alot more via the screw. You can set the idle limit to 2% or so.

  10. #10
    Lifetime Member minytrker's Avatar
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    Quote Originally Posted by slowhawk
    If the iac is at 170 then open the TB alot more via the screw. You can set the idle limit to 2% or so.
    If I open it more then the car will start but it idles at 1500rpms and wont go down. I have not tried this since I installed the new tps sensor however.

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