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TBI gurus, answer this! UPDATED!!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Bubba Ray Boudreaux, Jul 4, 2001.

  1. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Just want to get some thoughts and opinions before I tear into things. I went WOT from a dead stop today and wasn't impressed. I've had better runs and 3/4 throttle. Here are details: '87 350 144K motor. 14x3 K&N open filter, plugs gapped at .35(recommended .45 but for smog purposes.....), stock exhaust except for Flowmaster with hole, ADS Superchip running 92 octane and +2 on timing at idle. Sounded like the hole in the flowmaster, but the power wasn't there like at 3/4 throttle. I've ran 9.5's 0-60 at 3/4 throttle, but at WOT it runs like crap unless I'm out on the highway. Thinking about pulling plugs and maybe going back to .45. In a couple of months, maybe 3 going to put on new cat with a Flowmaster 1 chamber. Could I be pulling in too much air for the computer to keep up? Just something that sounds like fun to fix, never cared about it in the past.

    "I am Republican. Not a baby-killing, tree hugging, land grabbing, touchy feely, hypocrite wuss democrat!"<P ID="edit"><FONT SIZE=-1>Edited by BRBoudreaux on 07/10/01 04:56 PM (server time).</FONT></P>
     
  2. CaptCrunch

    CaptCrunch 1/2 ton status

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    Re: TBI gurus, answer this!

    Ok just a stupid question here for some, but it seems like this gets by a lot of people... how old are the fuel filter, plugs, wires, cap, rotor...etc. Secondly I would definetly recomend a MSD coil and some high quality plug wires from MSD or Taylor. Open the plug gap to .060 and this will help improve the WOT I think. Does it seem to be running lean or rich? Another item, maybe set the timing back 2 degrees because I assume the chip gives you a bit more agressive advance curve for you ignition system (thus they say us 92) and you could be getting detionation even if you don't hear it. This would key off the knock sensor and automatically retard the timing big time. Keep posting details and info and I'm sure all of us can give you some ideas.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <A target="_blank" HREF=http://www.geocities.com/milnerlives_2000/blazer.htm>http://www.geocities.com/milnerlives_2000/blazer.htm</A>
     
  3. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Re: TBI gurus, answer this!

    Fuel filter and wires are almost two years old, but it was parked for almost half that. It's always ran like this at WOT, I just never have wanted to mess around with until now. I'm running MSD wires, but the coil, cap and rotor are stock. I'm thinking it's running lean since I have the open filter and the comp can't throw in enough fuel. Really wish I had an ALDL cable to hook into the laptop. After I put the chip in, I still had some '87 octane in the tank and when I got on the pedal, it would ping, but with the '92 it's gone away. Talked it over with my chief mechanic and he recommended backing the timing off. If I don't play golf on Saturday, I'll pull the plugs and check them out and regap.

    "I am Republican. Not a baby-killing, tree hugging, land grabbing, touchy feely, hypocrite wuss democrat!"
     
  4. 90K5

    90K5 1/2 ton status

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    Re: TBI gurus, answer this!

    It seems like most cars are faster at 3/4 than WOT...at least my K5 is, and so are my friends cars....just my $.02

    90K5

    See my truck at <A target="_blank" HREF=http://albums.photopoint.com/j/Albumindex?u=1329584&a=9886502>http://albums.photopoint.com/j/Albumindex?u=1329584&a=9886502</A>
     
  5. Panther

    Panther 1/2 ton status

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    Re: TBI gurus, answer this!

    From my experience (albeit small [​IMG] ), that seems to be the case in all stock slush boxes (regardless of air intake). 3/4 throttle seems to give you better accleration.

    <font color=blue>Brillance is like 4wd, it allows you to get stuck in a more remote location [​IMG]</font color=blue>
     
  6. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Re: TBI gurus, answer this!

    Try re-gapping the plugs to .045 (or .45 I can't remember if the zero is there or not, but I think it is). The reason being, the amount of air and fuel being let in by the throttle body, may not being completely burned at full throttle with the smaller gap. A TBI system uses feedback, but does have some inefficiencies compared to TPI and other EFI systems. The TBI system is more or less a fuel injected carbueretor. As stated before poor spark from a weak coil, bad wires, bad cap/rotor (if so equipped), O2 sensor/catalitic converter going south, etc. can all lead to poor performance and full throttle "choking".

    If you didn't build it yourself, how can you call it yours.......?
     
  7. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: TBI gurus, answer this!

    I hate to say it again, but the fuel pumps in those years suck @ss. You might want to go thru the trouble of swapping in a new one to see if that eliminates your problem. When my 88 started acting like that, a new fuel pump fixed 'er up quicker than quick.

    <font color=red> Check out my truck @ </font color=red>
    <A target="_blank" HREF=http://24.10.209.54/bigolk5.htm>http://24.10.209.54/bigolk5.htm</A> [​IMG]
     
  8. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: TBI gurus, answer this!

    Also, just for giggles, tear out the injectors and inspect the housings that they reside in. Mine had formed some sort of growth in them, requiring the use of a dremel to remove it! Ultimately, I put in new injectors too...

    Just my .02

    <font color=red> Check out my truck @ </font color=red>
    <A target="_blank" HREF=http://24.10.209.54/bigolk5.htm>http://24.10.209.54/bigolk5.htm</A> [​IMG]
     
  9. newyorkin

    newyorkin 1 ton status

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    Re: TBI gurus, answer this!

    Growth! LOL!!

    Ratch
    <A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A>
    **K5 - What more is there to life?**
     
  10. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Here's what I've done so far. Replaced O2 sensor a few weeks ago and this weekend regapped plugs to .045. Haven't tried it yet so I'll have to wait and see. Plugs looked good, a little brown, book said it was okay, it's some additive, OKAY!! Next step will be coil and cap, but that's down the road a little bit.

    "I am Republican. Not a baby-killing, tree hugging, land grabbing, touchy feely, hypocrite wuss democrat!"
     
  11. realsquash

    realsquash 1/2 ton status

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    Lose the chip and put your timing back to stock and I think your problem will go away. Most likely the ECM is getting knock counts which in turn retards the timing big time. It isn't your gap or your cap/rotor/etc.

    Squash
    <A target="_blank" HREF=http://www.trailrunners4x4.org/users/realsquash>http://www.trailrunners4x4.org/users/realsquash</A>
     
  12. realsquash

    realsquash 1/2 ton status

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    Re: TBI gurus, answer this!

    Um, mine is faster at 100% throttle...

    Squash
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  13. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Re: TBI gurus, answer this!

    Yeah, but don't you have an unfair advantage? I should hurry up and get the equipment I need to retune it. Just curious to compare this chip to the stock chip.

    "I am Republican. Not a baby-killing, tree hugging, land grabbing, touchy feely, hypocrite wuss democrat!"
     
  14. johnnysjimmy

    johnnysjimmy Registered Member

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    Re: TBI gurus, answer this!

    I also had the same kind of problem with my 88' sub. Once I got a fuel pump that worked (2nd) the problem was gone just my own experience

    73' GMC Jimmy 8" lift and 35" tires.....14 boltff and big 10 bolt on the way
     
  15. 502Burban

    502Burban 1/2 ton status

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    Re: TBI gurus, answer this!

    I'm with Krazie. You might want to look into a fuel pump that is up to providing enough fuel at WOT. A fuel pressure gauge that you can monitor while driving might be an eye-opener. Often, those stock pumps just can't keep the pressure up in WOT conditions.

    Robb
    '73 GMC Suburban - 502DFI
    <A target="_blank" HREF=http://community.webshots.com/user/robbrj>http://community.webshots.com/user/robbrj</A>
     
  16. KENT

    KENT 1/2 ton status

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    I have an 1989 with TBI. When I boought it it ran like your are describing. The former owner had set the timming to what he tought was correct. As I understand it the computer uses the timming as a base line to calibrate the rest of the sensors. Timming is supposed to be a constant.

    I re-timed my rig to the specs on the emmisions sticker and it made a tremendous difference. Just remember to disconnect the wire before you set the timming. I believe that it says which one on the sticker. Mine was a solid brown wire with a connector right over the brake boster.

    Kent

    1989 K5 33X12.5 with 2.5" lift 12 bolt with aubur posi running 3.73 gears.
     
  17. realsquash

    realsquash 1/2 ton status

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    Re: TBI gurus, answer this!

    If it's a fuel pump issue, it's not because it doesn't flow enough normally. A functional stock pump would be fine in his app.

    I still vote for knock counts.

    Squash
    <A target="_blank" HREF=http://www.trailrunners4x4.org/users/realsquash>http://www.trailrunners4x4.org/users/realsquash</A>
     
  18. realsquash

    realsquash 1/2 ton status

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    Re: TBI gurus, answer this!

    I know you don't want to hear this, but in your case the stock chip would be best. The hypertech chips for your truck that i've reviewed appeared ONLY to bump up the WOT timing and the WOT fuel adder. If you have a stock chip, stick it in and try it. I bet you'll be suprised!

    Squash
    <A target="_blank" HREF=http://www.trailrunners4x4.org/users/realsquash>http://www.trailrunners4x4.org/users/realsquash</A>
     
  19. realsquash

    realsquash 1/2 ton status

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    Re: TBI gurus, answer this!

    Not to start an argument, but a TBI is nothing close to a carb with injectors.

    Squash
    <A target="_blank" HREF=http://www.trailrunners4x4.org/users/realsquash>http://www.trailrunners4x4.org/users/realsquash</A>
     
  20. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Re: TBI gurus, answer this!

    I just stuck this ADS chip in, kept the stocker since this one is not smog legal. I just curious, plus the $25 I paid for it wasn't that big of a hit. So far the only difference I've noticed is gas price since I have run premium. Two things I've noticed with this ADS chip is harder starting and when I first got it, still had some 87 octane left so it was pinging under load. Got it for a comparsion to the stock chip when I get the ability to look at that stuff.

    "I am Republican. Not a baby-killing, tree hugging, land grabbing, touchy feely, hypocrite wuss democrat!"
     

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