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Strange TBI Lack of Power

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by AZ_Overdrive, Jan 6, 2003.

  1. AZ_Overdrive

    AZ_Overdrive 1/2 ton status

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    My 89' Burb has a strange lack of power issue. Has anyone herd of or had this problem...

    The truck will accelerate normally with moderate pedal pressure. But when trying to pass or floor it the engine does not respond. It acts as though the pedal is only being lightly applied. Any ideas?

    The transmission is down-shifting correctly, into and out of overdrive. I can even feel the converter locking and unlocking but the power band on the engine is FLAT. It doesn't even rev while stomping the pedal.

    It has been hooked up to an analyzer but all systems report OK.

    Any assistance would be appreciated.

    Thanks,
     
  2. HarryH3

    HarryH3 1 ton status Author

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    Did it start this suddenly? I had a similar problem with my '87 K5 once, during a long trip. I stopped and swapped the fuel filter, but no help. But I stopped to refill the fuel tank a while later and the truck starting running correctly again within a half mile of leaving the station! The previous tank of gas was junk, had water in it, whatever. /forums/images/graemlins/mad.gif
     
  3. TopOff

    TopOff 1/2 ton status

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    Sounds like a vacuum leak....

    I had the same problem when I first put my TBI on mine... heheh I forgot to tighten down the TBI unit. /forums/images/graemlins/laugh.gif

    Could also be a bad O2 sensor, bad knock sensor, bad ignition unit.

    "Ask" the computer what's wrong.

    Good luck.
     
  4. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    I've had the same problem, fuel filter. It's the cheapest place to start.
     
  5. AZ_Overdrive

    AZ_Overdrive 1/2 ton status

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    It's been about 6 months since I replaced the fuel filter. I also will try the O2 sensor and a new coil. I will check it out this weekend.

    It has been behaving like this for a while. It may have been as long as I have owned the truck, just never noticed it (driving around like an old lady!).

    I would think if there was something wrong with one of the ECM monitored systems that it would flash a code... Is that an incorrect assumption?

    I was thinking it might also be the TPS since that is what tells the computer where the throttle position is, either at idle or WOT...

    Thanks for the input, hopefully I can figure this one out.
     
  6. Does it have a cat converter on it? Make sure it's not plugged up, and check your muffler for internal blockage. I've seen some mufflers break loose internally and restrict air flow before the muffler itself blows.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes assuming ECM would flash codes would be an incorrect assumption. What do you think monitors the O2 sensor? I'm sure there is a code for ignition too.

    If you plan on keeping it, think of getting a scanner for it, something like an autoxray 240. You'll need the service manual too. You can test things like the TPS (which I was thinking needs tested anyway...TBI guys will know if you can adjust it, I'm guessing yes) yourself of course, but a good scanner lets you see whats going on real time.

    You are fooling yourself if you think it is too expensive to go the diagnostic route.
     
  8. RockyRider13

    RockyRider13 1/2 ton status

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    The thirdgen.org? site has information on how to tune your tps.
     
  9. BigBurban350

    BigBurban350 1/2 ton status

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    Hook up the scanner and monitor the O2 sensor. The truck should enter closed loop when it heats up and the O2 voltage should toggle continuosly above then below 500 milivolts like from 200 to 800 to 200 to 800. If it is not toggling the truck wont enter closed loop therefore depending on the TPS and MAP sensors to determine the correct air/fuel mixture which is not as efficient as the O2 so the truck becomes retarded. /forums/images/graemlins/usaflag.gif /forums/images/graemlins/burb.gif /forums/images/graemlins/usaflag.gif
     
  10. tori89k5

    tori89k5 1/2 ton status

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    Save yourself the dough, its not the coil. They dont cause symptons like that when they fail. All you need to test the TPS is a voltmeter. Set it to an Ohm setting, and connect the leads to two of the terminals on the TPS. Rotate the TPS trigger real slow and watch the needle/digital display. It should increase/decrease evenly with no spikes, or breaks in the reading.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    You've gotta know the correct voltage values for TPS, as I recall there is a base value and WOT value that needs to be met, along with of course, smooth change in resistance as throttle is applied.
     
  12. GRINCH

    GRINCH 1/2 ton status

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    Dorian is correct!!!

    You need to check the voltage on the sensor. With engine off and key on you should see 0.42-0.48 at idle no pressure on the peddle. At WOT you should see 4.55-4.85 volts. Another awesome scanner I use is fromthe buick GN world called Turbo-link. It works on 86-91 chevy/gmc trucks-blazers.

    Check it out here..

    Turbo-link /forums/images/graemlins/thumb.gif

    Dennis
     
  13. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    That software looks kewl! Too bad its $250! Damn... Think I'll stick to WINALDL... /forums/images/graemlins/thumb.gif

    -Dan
     
  14. AZ_Overdrive

    AZ_Overdrive 1/2 ton status

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    Wow! That WINALDL looks pretty cool! Will it perform the same functions as the other "Live" scanners?

    It seems to me, based on what people here are saying, that it is imperative that I have a live data type scanner. It sounds like the must-have tool for a TBI truck. I will check out the free WINALDL and look around for the other type of scanner.

    Thanks for the valuable input. Hopefully I can get the Burb running well again. It is a shame to not have any power with a FF in the rear!
     
  15. Burbinator

    Burbinator 1/2 ton status

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    I had to use a program called DataMaster from TTS Power Systems on my truck, due to 1) the baud rate and 2) WinALDL will not work with powertrain ECM's. You might want to make sure that your ECM baud rate is 160 or ALDL will not work. A quick and easy way to know for sure is whether or not you have an electronically controlled transmission (8192 baud) or conventional transmission (160 baud).

    /forums/images/graemlins/burb.gif
     
  16. AZ_Overdrive

    AZ_Overdrive 1/2 ton status

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    Trying to make the Software Work

    KRAZIE87K5
    Did you make your own data cable?? I spent the last 4 hours creating the cable (circuit) on the web site but no go on the program reading any data from the truck's computer. Is there a certain sequence of things to get it to work? The instructions are minimal..

    Your help would be appreciated!
     
  17. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: Trying to make the Software Work

    Truth be told, I didn't make my cable it came with the fuel injection system! /forums/images/graemlins/cool.gif Sorry to be of no help... where have you found info to make the cable? Maybe I could help by looking at that info, and then looking at my cable? Let me know if you would like me to help.

    -Dan
     
  18. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: Trying to make the Software Work

    Ok, after looking I found the diagram right in WINALDL's site! /forums/images/graemlins/blush.gif So....

    [​IMG]

    Looking at that, I can already tell you one thing I notice. My cable has only two pins that connect to the ALDL conn, on pins A and E. So with regard to <font color="blue">R3</font color>, my cable uses it in the "open" mode.

    Here is a pic of my cable:

    [​IMG]

    Hope any of this helps! /forums/images/graemlins/wink.gif

    -Dan
     
  19. tori89k5

    tori89k5 1/2 ton status

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    sorry guys..... was only giving him a quick easy way that "anybody" could check their TPS. True, its only a partial check, basic - to see if it had an open. Was only ment to be a quick walk out to the truck an check test. /forums/images/graemlins/crazy.gif
     
  20. AZ_Overdrive

    AZ_Overdrive 1/2 ton status

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    Helps out a ton!! But still have questions.

    Interesting that you only use "Open" mode and not ALDL... I have a couple of specific questions if you please...

    1. How, exactly, do you hookup and run the WINALDL software (step by step please. ie. plug in wires, start ignition, rev motor... etc..).

    2. With your "open" setup do you still receive live data (rpm and voltages?).

    3. What year and model (and engine size) of truck are you running this on.

    Thanks for the help. The schematic you posted was the same one I followed to create the cable (in ALDL mode). I sure hope I can get this working!

    Thanks, again.


    P.S. This would be a good tech topic for someone to write for the K5 website...

    /forums/images/graemlins/burb.gif
     

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