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Computer in TBI?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by civicstomper, Jan 4, 2004.

  1. civicstomper

    civicstomper 1/2 ton status

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    Hi, my truck is still running rough, and this is after changing spark plugs, ignition wires, distributer cap, rotor, vacuum lines, gas lines, fuel filter and fuel pump. it is better, but it still runs rough frequently. for example, yesterday backing up a very small incline, it quit on me, but started up again fine. this is not the first time its doen this, and as my DD, i would like to get all the big problems worked out.

    anyways, my truck is an 87 K-5, 350TBI. Now I know 86 was the last year for carbuerators and I know that around the early 90's more things started being computerized. Does anyone know what is computerized on an 87 vs what is not? i am reading up on TBI now, my friend has a code scanner, but if anyone know/ knows were i can get a list as to what is computerized, that would be greatly appreciated.

    If anyone has had similar problems after trying to fix similar things and has any ideas at all, that would be great. Thanks!
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    far as I know all the TBI systems in our trucks are the same basically. Maybe it's a bad sensor, how many sensors have you changed? When was the last time your o2 sensor was changed?
     
  3. bigburban383

    bigburban383 1/2 ton status

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    Could be a sensor like the MAP sensor. If it happens on cold start ups the computer relies on other sensors like the TPS (throttle position sensor) and the MAP sensor (manifold absolute pressure). If you know somebody with a real scanner you can check the sensors to see if they are in range. If not just replace the MAP and TPS, they shouldnt be expensive ether. Good Luck /forums/images/graemlins/thumb.gif
     
  4. R72K5

    R72K5 Banned

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    clean the IAC and have the ignition module tested, also wire from the coil to DIS are known to go bad and break inside insulaton and cause random dying and no restart alot,

    TBI is TBI,

    O2, MAP, TPS, IAC, DIS, knock,
     
  5. civicstomper

    civicstomper 1/2 ton status

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    I actually havent changed any of the sensors yet. I got the truck used, so I dont think the o2 sensor has ever been changed. Is there any indication at all of when this happens, such as the "check engine"? Thanks for the advice!
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  6. civicstomper

    civicstomper 1/2 ton status

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    hmmm, that makes since too. see, my friend with the scanner was saying something similar to the TPS but I wasnt sure. I could also check the MAP too, they both sound like one of those kinds of things worth replacing. Thanks for the help!
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  7. civicstomper

    civicstomper 1/2 ton status

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    hmmm, i hope this doesnt make me sound dumb, but what does DIS and IAC stand for? If its known to cause random dying and no restart then that also sounds a lot like my truck /forums/images/graemlins/thinking.gif
    well thanks guys, i have a lot of good information now that I can use when I make my big trip to Autozone bright and early tomorrow morning /forums/images/graemlins/cool.gif
    I'll let you know how it turns out and thanks again!
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  8. TopOff

    TopOff 1/2 ton status

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    You can jumper the A&B wires in the ALDL connector. Your Check Engine Light will flash a code. This code can tell you what sensor is "out of range" and is most likely the culprit.

    Check a Haynes manual.

    Good luck.

    BTW: If you REALLY want to watch what your F.I. computer is doing and you have a laptop, and are good with soldering electronics - check out www.moates.net and click on his ALDL config/setup.

    Have fun!
     
  9. civicstomper

    civicstomper 1/2 ton status

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    yeah, that sounds like what i will have to do. i have been doing some reading and it all sounds like the sensors mentioned. Oh, thanks for that website! My dad is better at soldering and electrical work than me, and he thinks he can make that thing, so that will probably come in handy. Thanks again, and i'll keep you guys posted /forums/images/graemlins/cool.gif
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  10. TopOff

    TopOff 1/2 ton status

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    BTW: I bought a generic circuit board at radio shack for $4 to make mine. But I had to go to a "real" electronics store to get the MAX232-c chip.

    Have fun
     
  11. k5moneypit

    k5moneypit Registered Member

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    I've had the random dying and not starting problem,many times. Knowing what I know now, I would say ignition Module. They go bad and dont send out a check engine code. The reason I ended up replacing around 7 of them, after being stranded many times, was alternator back feed. After contacting the ignition module company and changing the alternator, Its been almost a year and no problems. Also check for a prom update on your computer at the dealer. That is also an idea. Hope ya get it fixed.
     
  12. civicstomper

    civicstomper 1/2 ton status

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    hmmm, that was along the lines of what my dad was thinking too; the ignition module. it looks like i will be replacing everything on this truck now, so i might as well fix anything that could be a potential problem. Thanks for the advice!
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  13. reeser

    reeser 1/2 ton status

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    [ QUOTE ]
    Could be a sensor like the MAP sensor. If it happens on cold start ups the computer relies on other sensors like the TPS (throttle position sensor) and the MAP sensor (manifold absolute pressure). If you know somebody with a real scanner you can check the sensors to see if they are in range. If not just replace the MAP and TPS, they shouldnt be expensive ether. Good Luck /forums/images/graemlins/thumb.gif

    [/ QUOTE ]

    i know for a fact it's the MAP sensor, i had the same probs and i replaced every single one and nothing happened til the magical MAP sensor!!!
     
  14. MA87K5

    MA87K5 1/2 ton status

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    You can also try replacing the EGR valve. I have an 87 k5. There is a way that you can check the EGR. It should be in either Haynes and/or Chilton. I did the check and it checked out, so I disconnected the hose that goes to the top from the MAP to the EGR and the surging and stalling went away but couldn't pass emissions so I bought a new one and haven't had a prob yet, it has been a couple of years. A bad EGR doesn't always give a code. It could give a bad MAP code though. Check the parts before you spend more $$. The only code that I got was 44. The easiest way to check the ignition module is to bring it to a parts store and have them check it.
     
  15. civicstomper

    civicstomper 1/2 ton status

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    Really? That is seeming to be it more and more, ive been getting a lot of ansers and doing a lot of reading, and mostly everything is pointing to that MAP sensor. So then do I just get a new one? Because if that was all that was required, that would be great. Thanks for the advice /forums/images/graemlins/thumb.gif
     
  16. civicstomper

    civicstomper 1/2 ton status

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    Hmmm, so you're saying I can check the EGR and the MAP sensor by disconnecting the hose from the MAP to the EGR? That makes sense. Now, if the surging/stalling does go away does that mean I have it narrowed down to the EGR, or could it still be the MAP? ill try that first and see what happens. I'm going to try to find my Dad's Chilton book and see what they say as well. Thanks for the advice, and i'll keep you guys posted
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  17. civicstomper

    civicstomper 1/2 ton status

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    Re: Computer in TBI? *Update

    Hey, sorry its been so long. My Dad's Yukon has been having problems so its been getting a little busy.

    I looked around under the hood and found all the sensors and made sure they had good connections. My friend did have a scanner, but the only problem was that it only covered up to 1985 Chevy trucks and mines an 87. I tried it anyways, and it said that the reading for the MAP and the O2 sensor were Not Available. I tried disconnecting the MAP and attempted to start the truck and it didnt like that at all.(wouldnt start).

    I then drove the truck down the road with my friend reading the scanner, and then the MAP and O2 sensor were seen and reading properly. Again, being not the right year scanner, some of the readings may be inaccurate.

    I bought a Hayes manual and I am probably going to get a new scanner that covers and '87.

    Sorry this is such a long post. Thanks for all of the help, this is my first time doing sensors and this would have been a lot more confusing if it wasnt for all the information I got here. Thanks again, and I'll let you know how it goes.
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  18. BurbinOR

    BurbinOR 3/4 ton status

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    Re: Computer in TBI? *Update

    [ QUOTE ]
    Hey, sorry its been so long. My Dad's Yukon has been having problems so its been getting a little busy.

    I looked around under the hood and found all the sensors and made sure they had good connections. My friend did have a scanner, but the only problem was that it only covered up to 1985 Chevy trucks and mines an 87. I tried it anyways, and it said that the reading for the MAP and the O2 sensor were Not Available. I tried disconnecting the MAP and attempted to start the truck and it didnt like that at all.(wouldnt start).

    I then drove the truck down the road with my friend reading the scanner, and then the MAP and O2 sensor were seen and reading properly. Again, being not the right year scanner, some of the readings may be inaccurate.

    I bought a Hayes manual and I am probably going to get a new scanner that covers and '87.

    Sorry this is such a long post. Thanks for all of the help, this is my first time doing sensors and this would have been a lot more confusing if it wasnt for all the information I got here. Thanks again, and I'll let you know how it goes.
    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif

    [/ QUOTE ]

    About $150 will buy you an Auto Xray www.autoxray.com that will do the job if you don't want to build a cable/get a laptop/download winaldl. I use the Auto Xray and am pleased with it.

    Good luck.............
     
  19. XHitman396

    XHitman396 1/2 ton status

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    Re: Computer in TBI? *Update

    i will also say ignition module, mine was randomly dying and so i changed: 2 coils, wires, plugs, fuel filter, rotor, dist. cap, and then had ignition module checked, oreilly's said it was good, but as last ditch effort, changed it, and badda bing, no more dying in last year, since i got the new one...
     
  20. MA87K5

    MA87K5 1/2 ton status

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    That is what I did and the surging went away. I also changed the MAP with a new one before I disconnected the
    EGR and no change. Luckly I knew someone who worked at the parts store so the swap was temporary, didn't cost anything.
     

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