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Bad idle problem.... help fast please.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jpaitala, Sep 11, 2003.

  1. jpaitala

    jpaitala Registered Member

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    Today my '89 Blazer(350) went nuts...
    The idle is horrible or I think I can say there isn't any idle. Without pushing the gas pedal the car dies, keeping the RPM's over 1500 everything is fine but under that, coughing, missing etc etc.
    I cannot find anything, the only code is 12(everything should be ok?!)...
    The only symptom is that I think is that it's runnign too rich, because after a little "RPM-session" there's smoke
    coming behind the injectors.

    Any ideas would be real helpfull!!!

    Thanks.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Burnt through plug wires, disconnected vacuum lines, broken/disconnected engine control wires?
     
  3. jpaitala

    jpaitala Registered Member

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    What about the symptom that it's running rich, normally at idle I have never seen injectors to inject so much fuel as my Blazer now does. There's a real lot of fuel coming through now...
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    I didn't understand the "smoke behind the injectors comment", so I wasn't sure exactly what you meant.

    I'd still inspect for loose or bad wires, especially the idle air control. (IAC)
     
  5. jpaitala

    jpaitala Registered Member

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    The smoke is light smoke, smells like gas mostly. The smoke looks similar to carburated engine with too rich mixture. The smoke only appears when I shut the car down.
    This is real annoying, because I bought this car 8days ago, and havent really driven it, because of all the repairs it needed. Now when everything is done, it wont run anymore and I should be able to get to the yearly inspection on saturday morning with the blazer.
    Just to be sure that there's no misundestanding, the repairs had nothing to do with the engine bay, interior and exterior repairs only.

    Thanks.
     
  6. Silverado_K5

    Silverado_K5 1/2 ton status

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    Did the fuel pressure regulator in the TBI go out?
     
  7. FWP

    FWP CRS

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    Try this, run the fuel pump using the test connector, with the engine off. There shouldn't be any fuel coming out of the injectors.
     
  8. jpaitala

    jpaitala Registered Member

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    The last two posts are "promising", but could someone be a little more specific what to do??
    I havent done any "EFI-tuning" previously.
     
  9. jpaitala

    jpaitala Registered Member

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    It's simply runnign too rich. Immediately when I unplugged the connector for one of the two injectors the idle came back to normal. It doesn't matter which one is off, as long as the other injector is out the idle is normal. If I plug both injectors on, then the problem comes back.

    Any suggestions??

    Thanks.
     
  10. jpaitala

    jpaitala Registered Member

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    It's not the spark plugs, not the plug wires...
    Every hose and connection is checked, but nothing helps.
    I'm desperade, what can I do??? /forums/images/graemlins/frown.gif
     
  11. azblazor

    azblazor 1/2 ton status Premium Member

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    You need to put a scanner on it. It should be throwing a code given your symptoms but if it isn't then a scanner will read each sensor's data. You can only easter-egg it so much. You may have a bad O2 sensor that is telling the computer to dump fuel, etc. If it's doing this in open loop control then you could have a bad ECM.
     
  12. jpaitala

    jpaitala Registered Member

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    The problem is "in here"...
    [​IMG]

    If I unplug this connection(as seen in this pic), everything is back to normal.
    What could be wrong here?

    Thanks.

    Ps. The scanner would be great, but nearest GM scanner is over 200miles away from me...(not an option really)
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    There is no choke on a fuel injected vehicle.

    Isn't that the EGR solenoid that grim was talking about?
     
  14. hardcore71

    hardcore71 Registered Member

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    What you have there is a bad MAP sensor (manifold absolute pressure). Check to make sure that there is engine vacuum at the sensor at idle. If so the sensor is bad. These are realitively failure prone and fairly inexpensive.
     
  15. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Ahh, that's what that is. I knew I recognized it from somewhere.

    Yep, MAP sensor is very important and luckily very cheap.
     
  16. jpaitala

    jpaitala Registered Member

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    Could bad MAP-sensor cause my Blazer to have bad HC-percentage on emission check?? I just got home from annual vehicle inspection and my blazer was rejected because of too high HC-percentage.
     
  17. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Absolutely. It tells the engine how much air is coming in based on vacuum and meters fuel accordingly. The O2 sensors measure it on the other end, but the MAP sensor gives the computer quite a bit of information, including being responsible for adjusting fuel mixture for the air temperature and density.

    Oh yeah, too much fuel means more HC. /forums/images/graemlins/smile.gif
     
  18. jpaitala

    jpaitala Registered Member

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    Thanks!!!
    I thought so too...
    I'll just have to order new o2-sensor and new MAP-sensor and see if the problem goes away. /forums/images/graemlins/smile.gif
     
  19. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Try the MAP sensor first. It's cheap ($15 or so). If the O2 hasnt been done in a long time I guess you could do it. Don't use a crappy Autozone one though, get a good one.
     
  20. jpaitala

    jpaitala Registered Member

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    Just thinking that shouldn't the trouble codes tell me something?? Or is it normal, that no codes are present and still major idle problems...
     

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