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Winning the TBI wars!

Discussion in 'The Garage' started by Wingnutt, Mar 3, 2004.

  1. Wingnutt

    Wingnutt 1/2 ton status

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    Me thinks I'm getting the upper hand at last! I put a new O2 sensor in this evening and didn't see a whole lot of differance, and ALDL was still showing flagged data along with the same 'ol error codes. /forums/images/graemlins/confused.gif

    I remembered that I yet to clear the old codes, so I disconected the battery while I ate then reconnected it and started it back up. Much better! After a bit of tweaking to reset the idle and TPS, things were even better.....except I still had a rich mixture flag and the O2 readings were bouncing again and the IAC was justing sitting there doing nothing. /forums/images/graemlins/angryfire.gif

    So after getting discouraged, I thought what the hail and dropped it into drive. Whao! Big differance! 02 dropped and stayed steady, rpm's steadied and the IAC started doing it's thing! /forums/images/graemlins/smile.gif

    All of which leads to this: Why does it idle rich? And why does the ECM set the idle rpm's so low(500)? /forums/images/graemlins/confused.gif

    And lastly, I haven't done a cold start since resetting the codes, but I've got my fingers crossed.

    Life is getting better! /forums/images/graemlins/peace.gif

    Thanks everybody! Y'all rock!
    /forums/images/graemlins/peace.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/peace.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/bow.gif /forums/images/graemlins/peace.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/bow.gif /forums/images/graemlins/peace.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/bow.gif /forums/images/graemlins/peace.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/bow.gif
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    What does the MAP sensor input look like?
     
  3. Wingnutt

    Wingnutt 1/2 ton status

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    Steady, I can't recall the exact voltage. I will check it Friday evening when I see what it does when I do a cold start.
     
  4. 1badv10

    1badv10 Registered Member

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    not to steal your post here but /forums/images/graemlins/1zhelp.gif.. my tbi 350 is idling @ like 1200-1400 rpm, and about 1000 in drive, any idea why it would idle so high.. /forums/images/graemlins/confused.gif i plan on trying a new three wire o2 sensor this week(cause of the long tube headers) maybe the correct a/f mixture at idle will help.. hope you got yours figured out
     
  5. bigburban383

    bigburban383 1/2 ton status

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    Your ECM is actually programmed to 500 rpms, or its just idling that low?
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    1badV10,

    I'd say you probably have a vacuum leak.
     
  7. Wingnutt

    Wingnutt 1/2 ton status

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    bigburban383

    Thanks, that explains the (what I consider) low idle speed. Now if I could only get rid of that hesitation without advancing the timing and having the pinging problems.

    1badv10,

    That's one of the reasons that I replaced mine. To save ya the trouble of reading all the posts concerning this fight, here it is in a nutshell. Mine had done that for years, steadly getting worse (1800prm idle in neutral). The reason was because the throttle shaft bushings were worn into an oval shape, and nobldy makes replacements. Finally I bought a Holley replacement and it is much better, except for the hesitation problem that I am trying to work out.
     
  8. bigburban383

    bigburban383 1/2 ton status

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    [ QUOTE ]
    bigburban383

    Thanks, that explains the (what I consider) low idle speed. Now if I could only get rid of that hesitation without advancing the timing and having the ping problems.

    [/ QUOTE ]

    Whoa, so was your ECM actually commanding 500 RPMS, or was the engine just idling 500 RPMS.

    Do you have good gas? Are your short/long term fuel trims in spec? Did you put on a new Distributor/Rotor/Ignition wires/Plugs/Coil? Buy an Air/Fuel ratio meter ($30-50), when you punch it, it should go very rich. Its easy to hook up, just the one wire ties in with your oxygen sensor wire.
     
  9. Wingnutt

    Wingnutt 1/2 ton status

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    Well not exactly 500, but about 650 in gear (850-900 in neutral).

    [ QUOTE ]
    Are your short/long term fuel trims in spec?

    [/ QUOTE ] huh? whatz that? /forums/images/graemlins/dunno.gif

    Aldl is no longer showing a rich flag, but it still smells a bit rich.

    Yea all the ignition stuff is good (within 2 months). And I don't have an air/fuel ratio meter...yet.

    It is running good except for that dang hesitation when you open the throttle quickly. Actually it is acting like the timing is way slow.
     
  10. bigburban383

    bigburban383 1/2 ton status

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    [ QUOTE ]
    Well not exactly 500, but about 650 in gear (850-900 in neutral).

    [ QUOTE ]
    Are your short/long term fuel trims in spec?

    [/ QUOTE ] huh? whatz that? /forums/images/graemlins/dunno.gif

    Aldl is no longer showing a rich flag, but it still smells a bit rich.

    Yea all the ignition stuff is good (within 2 months). And I don't have an air/fuel ratio meter...yet.

    It is running good except for that dang hesitation when you open the throttle quickly. Actually it is acting like the timing is way slow.

    [/ QUOTE ]

    Fuel trim is just the computers way of controlling the fuel flow.

    I guess check the timing. You got to disable the auto advance.
     
  11. Wraparound

    Wraparound Registered Member

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    I want the analyzation abilities that you are describing. My 87 has had the same damned issues since I bought it six years ago. What do I need?
     
  12. Wingnutt

    Wingnutt 1/2 ton status

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    Get yerself ALDL, a cable and a computer and you will be set to see all the wonderful things that you computer sees. Theres a post on this page that that gives a link and where to get the cable.
     
  13. Hardcore

    Hardcore 1/2 ton status

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    [ QUOTE ]
    Theres a post on this page that that gives a link and where to get the cable.

    [/ QUOTE ]

    Where /forums/images/graemlins/dunno.gif
     
  14. Wingnutt

    Wingnutt 1/2 ton status

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    I guess it scrolled off the first page. Do a search for ALDL and I think you will leanr more than you want to know. /forums/images/graemlins/smile.gif
     
  15. BiggerRigger

    BiggerRigger Registered Member

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    Just a word of caution to the interface cable users. If you use a laptop to connect to your rig please make sure that the damb cable will hook up to your laptop! It took me about 3 hours to build the interface cable just to find out that it would not fit into the back of my laptop. So now Im back to square one. Or I could buy a new laptop! I checked with the dummys down at radio shack to find out if they had an adaptor to fit the db9 cable to the laptop and they just stood there with a puzzled look on there face so I gave up.
    Not to hijack but does anyone know where I could get an adaptor?
    Aaron
     

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