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Help with surging at idle on 90 burb TBI...

Discussion in 'The Garage' started by y5mgisi, Dec 19, 2006.

  1. y5mgisi

    y5mgisi 1 ton status

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    I just rebuilt the motor as many of you know. Now i have a problem with surging at idle. It only does it in gear, like if you stop at a stop light it will run /idle just fine for about 30 seconds then start to do this wiered up-down surge where it tries to die then picks back up over and over but never actually dies. The truck is throughing a code 33 that i cant seam to figure out. I took the truck up to a parts store here in portland that has one of those hand held scan tools(autoxray 6000) It has a funvtion where you can whatch what all the sensors are reading but it didnt show map. So here is the stuff that i got from it; this is running at idle in park
    promID: 4551
    IAC:39steps
    temp:165.2
    open loop
    TPS: .62 volts
    Intergrater: 128
    O2:448mVolts
    Knock: 0
    Block learn: 126
    o2 cross count:174 and rising quickly.

    Does any of that strike anyone as odd? I really would like to get this surge problem out of my hair.
     
  2. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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  3. y5mgisi

    y5mgisi 1 ton status

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    In my particuler case its going to be a map problem not a MAF Someone else allready posted that link before and ive done it all with no real conclusion. The only thing i havnt been able to do is see if the map is reading .1volt or less.
     
  4. scooter122983

    scooter122983 1/2 ton status

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    take a multimeter to the map and check it there if you cant get it on the scantool
     
  5. y5mgisi

    y5mgisi 1 ton status

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    Really? Do you hapen to know right off hand which wires i should probe?
     
  6. scooter122983

    scooter122983 1/2 ton status

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    Not off hand as im currently at work and do not have acess to my haynes book but im positive they cover it in the emissons section.
     
  7. y5mgisi

    y5mgisi 1 ton status

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    Maybe this would help?
    [​IMG]
     
  8. HarryH3

    HarryH3 1 ton status Author

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    With the scanner, check to see that the Park/Neutral switch is operating properly. It can cause strange idling problems if it isn't telling the ECM the correct mode.
     
  9. mr.smartass

    mr.smartass 1 ton status Premium Member

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    Are you running anything aftermarket like headers or anything?
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd say signal at "B" is where you'd look for the right voltage.

    Autozone's scanner should show the MAP AND P/N switch, my Autoxray XP240 does, and it's only probably 10 years old lol. :)
     

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