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90 r1500 subruban acting up.... Help

Discussion in 'TBI & EFI Conversions' started by Vbb199, Aug 25, 2019.

  1. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    OK, so I'm not very good with the later model tbi Trucks, just simply because I haven't had to mess with them much... They're fairly trouble free... I just know the basics...

    So today, my trucks started stuttering really badly... I can't accelerate very much from a dead stop before it starts jerking and stuttering.....

    I had to limp it home so on the way there, I would have to build speed from 1st without putting the pedal down very hard.. Once I got up to 55 or so, if I tried to stomp it, it felt like it would kick down to 1st again, except it felt like the motor wasn't even engaged to the transmission in a way.

    Immediately my first thought was the torque converter.. After limping it home. I let out the kids and family... Tried to fire it back up, it wouldn't even fire back up, after fighting it, I finally got it running again....

    Pulled it around back to the work area.

    Here's what I know.... Fuel is making it to the motor, it's flashing like it should in time with the motor, and accelerating like it should if I Rev it up... It will Rev up in park, all the way up to 5000, or whatever speed.

    It doesn't idle worth a damn at all.

    That initial stomping it from a dead stop and not wanting to take off but "slumping" made me think it was a vacuum leak immediately.


    Can anyone suggest anything to help me? A little clueless.

    Waiting on the motor to cool off to check spark plugs also.


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  2. Arkansas_V8

    Arkansas_V8 Proud Redneck

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    Coolant temp sensor if it's running rich and that's what's causing this.

    Sounds more like you have a bad TPS(throttle position sensor).


    Jump the OBD port and see what codes you get.
     
    BBBURB and 78C10BigTen like this.
  3. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    If I start it cold and it doesn't misbehave, does that prove that theory?

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  4. Arkansas_V8

    Arkansas_V8 Proud Redneck

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    Pretty sure it would read bad even on a cold start.

    Google how test tps, and cts. Both simple.
     
  5. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    Changed sparkplugs while I was at it, fired it up cold, now it idles like it's got a .900 lift cam in it lol

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  6. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    However it was idling about the same earlier.

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  7. C10MixMaster

    C10MixMaster Full Access Member

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    changed plugs and now its running worse.. first recheck you plug wires did you cross a set? factory plugs or racing plugs? go back to factory style plugs if there not. now the original problem no power. check your fuel pressure. the pumps a week to begin with and regulators are problematic to. A common cause for what you describe is a plugged fuel filter. if in doubt just change the filter it may cure your issue.
     
  8. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    I did plugs 1 wire at a time, OEM plugs, nothing fancy. However to be sure, I did check plug order, it's all the same. I can see the fuel spraying like it should In time with the motor still, but for sure, the problem has gotten worse, I can only assume because it's cooled down now. It was acting pretty much the same way earlier when I was driving it.. Barely able to run.

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  9. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    Was going to check throttle position sensor, just change it out with a good known working on... Bolts snapped right off in the TBI unit... So now I'm drilling and tapping it out to a little bit bigger bolt...
    Day just keeps getting worse

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  10. Arkansas_V8

    Arkansas_V8 Proud Redneck

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    Sorry man. I know how you feel.
     
  11. Arkansas_V8

    Arkansas_V8 Proud Redneck

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    Make sure to set the tps, and make sure it reads smooth from closed throttle to full throttle.
     
    Last edited: Aug 25, 2019
  12. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    Tried intake temp sensor.... Nothing better... Still not running. I'm not really sure what to do at this point.

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  13. Arkansas_V8

    Arkansas_V8 Proud Redneck

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    Did we try the TPS already?


    It only has so many sensors. Its basic.

    You are getting fuel, good spark, air.

    Why cant we pull codes?
     
  14. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    I'm scared to pull the tps off the other suburban after the bolts snapped off

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  15. Arkansas_V8

    Arkansas_V8 Proud Redneck

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    Test yours. Procedure on Google, and YouTube for how.
     
  16. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    Does .63 sound like a reasonable voltage with the throttle plate closed?

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