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o2 sensor going bad?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by asterix, Jun 8, 2004.

  1. asterix

    asterix Registered Member

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    While the k5 is in nutral or park it is find but the minute i but it in drive and hold the brakes it feels like it wants to stall. it drives fine and sometimes it smells like it is running rich. I did a search for rough idle and o2 sensor and found a lot of nothing.

    Brett
     
  2. rocko

    rocko 1/2 ton status

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    Is the "SES" Service Engine Soon light on?
    Could be a IAC valve... Idle air control valve...
     
  3. asterix

    asterix Registered Member

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    the only time that the light comes on is when i gun it on the highway and it gets a 43 error stating that the knock sensor has a low voltage.
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If you think it is running rich it probably is, or is not burning all the fuel.

    Has it been tuned up recently?
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    bad cannoter valve and the hydrodynamic flux capaciter has smoked the muffler bearings.

    read my sig. /forums/images/graemlins/rotfl.gif
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    bad cannoter valve and the hydrodynamic flux capaciter has smoked the muffler bearings.

    read my sig. /forums/images/graemlins/rotfl.gif

    [/ QUOTE ]

    /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    In all seriousness I guess your talking about a 87-91 350 equiped K5....It would help if you include this little morsel of info in your post. /forums/images/graemlins/deal.gif

    Doesn't sound like it's going closed loop. Time to grab a manual and do some testing. It's far to much info to even begin to try to explain here. There is a way to see if the ECM is in closed loop by jumping the ASDL port under the dash. I just don't recall the procedure. Once it is known if this failure is happening in closed or open loop then it's on to the next test. I really suspect that it's still open loop since it sounds rich. It's basicly like the Choke is still on if it had a carb.

    Next thing I would do is start looking for simple stuff like bad connection at the coolant temp sensor for the ECM. On my 454 that's in the front of the intap below the water neck. Should be about the same location on a 350.

    If the truck is in closed loop the shut it off put it in drive and see if it will start in drive. It should do nothing when you turn the key.
    The point of that test is I recall reading that the ECM is signaled when it's in gear or out. The ECM then makes and adjustment to compensate for the load. As I recall it uses the signale from the Neutral safety switch that Allows it to start.

    Get back with us once you do those tests and check that temp sensor.
     
  8. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    The O2 sesnor should be switching rich to lean. Its really easy to see if its working with a Vantage. You can also do the propane test, but then again you need the Vantage. I suppose you could use a DVOM, just backprobe the O2 sensor and see if its switching between 200Mv and 800Mv
     
  9. realsquash

    realsquash 1/2 ton status

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    Unless the engine is running you will not see the O2 swinging at all during your tests. The only thing this will tell you is if it's in open loop or not. The engine should not stall and run rich even if it is in open loop. Do you have any engine mods? Do you have a SES light on? We need more info to be able to help you out... It's the only way to avoid throwing parts at it for no reason.

    If it's stock I'd say you've got a disfunctional IAC, possibly an O2 sensor. Just about anything else will set a code, so check those out.

    Andy
     
  10. asterix

    asterix Registered Member

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    sorry about the vague discription. The engine is a fuel ingected 350 that has been bored over .30. I jsut bought it a couple months ago so I'm still learning about this beast. I upgraded from a jeep cherokee and am not looking back. i know that he put a new cam in there but not sure about the info on it, and the gold rockers, with a valve job. it has a single exhaust throught the cat then it becomes a dual. I have checked the plugs and rotor and they all look good and clean. It drives sweetly but i'm slowly going through and correcting little things. The transmission jumps a little from first to sec and someday I'll take it in for that, jsut a little above my head.
     
  11. realsquash

    realsquash 1/2 ton status

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    Ahhhh... This is what I was afraid of. I think what you're looking to do is tune it, I doubt there is anything wrong with any components unless it never ran this way before.

    Andy
     
  12. Thunder

    Thunder 3/4 ton status

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    In my opinnion If you like, and plan on keepind a FId truck. The best thing you can do right now is to get a Scanner like an Auto X Ray.($150.+-) Or if you have a lap-top You can download Clicky:Win-ALDL for free. And build or order a cable.
    A scanner will give you the codes and operating data you need to diagnose problems. It will save you a lot of money,time and frustration in the long run.
    Even if the data doesn't make sense to you now. You can post the numbers/data here and someone can help you out.
     
  13. asterix

    asterix Registered Member

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    sweet thanks for the link, he had one of the cheap scanners that you jsut plug in and gives you numbers, and i'm trying to track that problem down. it ahs to do with the knock sensor. But i'm not sure that has to do with the running rich. that cable will be easy to make
     

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