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Idle problem - coincedental to shop service?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by kim tate, Mar 12, 2000.

  1. kim tate

    kim tate 1/2 ton status

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    I put my '87 K5 in the shop for an emissions test. The report was hydrocarbons were too high to pass the test. Shop thought replacing the leaking TBI unit gasket would lower the numbers. I gave the shop the OK and the work was done. Hydrocarbons dropped and the truck passed the emissions test. Driving the truck home it failed to idle. Runs strong at all RPMs but stalls at 9 out of 10 stoplights. It rarely stalls if in nuetral and coasting. Seems I must be sitting still for it to quit. After it stalls, I hear the fuel sending unit run for about 2 seconds. It re-starts every time with just a bump of the key. I checked the ECM for trouble codes when I got home. Code 42 (Elec. Spark Timing) was in memory. I removed/cleaned every connectin within site of the EST and then reassembled all with dialectic grease. Removed the battery cables to erase ESC memory and cranked her up. No more codes in memory, but still will not idle. Seems to be more a problem after operating temperature is reached. It is no longer fun, balancing my feet on clutch/brake/accelerator pedals on the hills of Virginia! Anybody have any suggestions? Thanks.
     
  2. Jason73K5

    Jason73K5 1/2 ton status

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    Maybe a sticky Idle Air Controller valve? Try some carb cleaner on the throttle body.
     
  3. kim tate

    kim tate 1/2 ton status

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    Idle Air Control Valve

    Jason, I cleaned the IAC valve with BG air intake spray cleaner. Changed the fuel filter too. Still have a stall problem. Give me something else to do, I'm good at following orders!!
     
  4. Mr Red

    Mr Red 1/2 ton status

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    Hey Neighbor,

    Have you talked to the folk that did the work to begin with??? That's where I'd go. I'm sorry I don't know much about TBI or I'd drive over to help. Go ask the folk that did the work!!!! Sounds to me like they created a problem for you. In my line of work, I've had the opportunity to work w/ a lot of dealer Service Dpt Mgt. people. Unfortunately, they're mostly F@#% dealers but they are good people that know vhicles. Shoot me an email if you want to maybe get an opinion from someone at Ted Britt.

    <font color=red>David, '86 K5</font color=red>
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Have you checked the pressure in your fuel lines? Maybe your fuel pump is getting weak and you're getting a vapor lock.
     
  6. kim tate

    kim tate 1/2 ton status

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    Heh David, nice to hear from you again. The shop that did the work handles more than a dozen cars for my employer. Always get top service from them and they allow me to borrow tools (that says a lot)! I talked to them and the TBI gasket job was unremarkable. Also, my best friend is in the auto service businesss and I know first hand how often a new problem develops after an unrelated service is performed. The customer always thinks the shop F*&*-up and that is not necessarily so. I'm going to check the fuel pressure and the EGR and see what turns up. Thanks for the offer to help and I may take youup on getting an opinion from Ted Britt if my efforts fail.
     
  7. turbo

    turbo 1/2 ton status

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    The old leak let in more air and the O2 sensor noted this sent a signal to brain box which compensated with more fuel.
    You fixed the leak and now have less air and less fuel with too low a idle setting.
    Cold setting compensates but once warms up and goes to sensor feedback you just don't get enough air/fuel flow to keep running.
    The throttle body has a screw set on the TB for idle that opens up the air butterfly just like a carb.
    Twist it so idles warm at 800RPM in drive with barke on or in neutral if manual and all should be OK.
    The O2 sensor will compensate for the incrased air flow with more fuel to keep mixture correect.
     
  8. turbo

    turbo 1/2 ton status

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    In the past with the air leak the idle was prob too high so someone turned the idle adjust screw to slow idle and now that air leak is fixed you have to turn it again to get suficient air flow.
     
  9. kim tate

    kim tate 1/2 ton status

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    Turbo, that makes plenty of sense. Explains why it started immediately after service performed. I made a hard copy of your suggestion and will look at the truck this weekend. Working 12 hour days this week, plus a three hour round trip commute. Not enough hours left in the day to eat, sleep, and read to the kids. Thanks and I'll let you know how things worked out.
     
  10. mudfanatic

    mudfanatic 1/2 ton status

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    I had this problem with my S10 for a while, after spending hundreds of dollars on diagnosis and parts I decided to get out old Chilton and starrt diagnosing myself. After a process of elimination my problem turned out to be a MAP sensor.
    HTH
    '77 K5

    <font color=red>mudfanatic</font color=red>[​IMG]
     
  11. kim tate

    kim tate 1/2 ton status

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    Turbo was right!

    For all who are interested, Turbo had the correct diagnosis and the proper remedy. Much thanks to him.
     

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