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TBI swap finished, now i need your help guys

Discussion in 'The Garage' started by white-rhyno, Jun 12, 2005.

  1. white-rhyno

    white-rhyno 1/2 ton status

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    Well,
    I finally finished the swap about three weeks ago and have been running into trouble, i have been trying my hardest to figure them out myself.... Now i need your help.
    Heres a little background information on my project. My motor already had tbi heads on it for the future swap. Old block, with tbi heads. THe cam is here Its all spanish to me but my motor builder thought it would work good.
    I had affordable fuel injection set me up with a custom chip and wiring harness. I had pulled all the other stuff on an 87 pick-up. There chip eliminated the egr, knock sensor, esc, and vss. Sure made it simple to put it all together.

    ANyway, my problems.
    First trip out i had no low end power. It would actually backfire through the tbi at full throttle and low rpms. (dont know actuall rpms, i dont run a tach). BUt it seemed to have decent high end power. I had the timing at 12 degrees inital timing. ANd the O2 sensor (3wire) about 8" down from the collector.

    Second time out. Moved the timing to 4 degrees. Lost a bunch of power.

    THird time out. Set timing to 16 inital. Moved O2 sensor into the collector. Ran a scanner on it. All seem to check out except the O2 sensor reading. Normally it would read about 400-880 mv. Sometimes it seem to stay at 004 mv. then pull a code 45 rich exhuast. Then pull a 44 lean....... Had way better power on the bottom end. But i could still get it to backfire through the tbi if the rpms were low enough.

    So, i guess my question is, how much inital timing can i give it??? just go till it pings?

    Also i have a wierd idle. It seems to "hunt" for an idle. Idle goes low, then back to normal. I was told vacum leak. I have checked twice now for leaks when it was cold with starting fluid. I cant find one...

    It does pull 16" of vacum at an idle.

    I have done everything but get a fuel pressure reading. Would that help?
     
  2. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Wow! Sounds like you've made things pretty tricky for yourself. The bad idle could be no vss and /or the cam (computers like a compatible cam). Usually you'd set the timing to zero with the advance wire disconnected. The ECU takes care of advance for you. I'd get on to Affordable if I were you as it's a bit of an odd set up that does away with vss, knock and egr etc. Maybe they can tell you where you're going wrong.
    Backfiring thru the throttle body I would have thought was too much timing and/or too much valve overlap on that cam.
    Good luck!
     
  3. dyeager353

    dyeager353 Banned

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    many things can be wrong. get winALDL and it will help you diagnose








    home page
     
  4. kgblazerfive

    kgblazerfive keymaster Premium Member GMOTM Winner

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    All my experience has been setting the timing to 0 with the vac. disconnected also. Second the opinion to go to the chip man. and talk to them.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    I agree with southernspeed. Knock sensor deletion seems like a bad idea, but VSS removal alone is just not right. VSS is tied into IAC among other things, removing it just doesn't make sense. You wouldn't be able to monitor vehicle speed through the ECM if it weren't needed.
     
  6. white-rhyno

    white-rhyno 1/2 ton status

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    ill try getting ahold of norm at afi and see what he has to say about my situation. Thanks.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Go over to jagsthatrun.com and search out the page where their VSS stuff is listed. It tells you why VSS is needed, particularly in conjunction with the IAC.

    As to ESC/knock sensor deletion, why? On a motor that isn't running on the ragged edge of streetability, I do not see any reason to remove a knock sensor. Yes they can pick up "false knock", but that's something you can monitor. If you aren't picking up false knock, why remove it, and if the engine IS knocking, now you will for certain hear it, long after it starts.

    Your cam is pretty darn mild, (although lobe sep. is pretty small) there shouldn't be much difficulty making that thing run good without deleting stuff GM saw fit to spend billions developing, and used on every TBI vehicle produced.
     

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