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Idling Problem, VIDEO inside

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by B_to_C, Jan 11, 2004.

  1. B_to_C

    B_to_C 1/2 ton status Author

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    info about truck:
    1990 GMC Jimmy, orignial 350 with 118,000 miles
    -first winter with TB spacer and k+n open element filter,
    -first winter in colorado

    problem is: when i start the truck up (this all started when it got cold out, but there may be no correlation at all) the idle bounces. it will rev itself up to 1100 RPM (Cold idle) then drop to 500 RPM (stall), and cycle like that until the engine warms up...I was thinking some sort of sensor? /forums/images/graemlins/1zhelp.gif

    Video: HERE
     
  2. 99firehawk

    99firehawk 1/2 ton status

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    My vote is the tbi gasket I used to have to replace the one on my van about every 5-6k miles, tb was warped I think. Gasket is about 4$ and take ya about 20-30 min to install your first time.
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    [ QUOTE ]
    -first winter with TB spacer and k+n open element filter

    [/ QUOTE ]

    Your truck is getting cold air at cold startup now that you've gone open element. The factory aircleaner system uses a vacuum controlled valve that directs warm air to the intake during cold weather starts. GM did this for a reason, brother.

    Ditch the open element and go back to the factory aircleaner setup. Open elements can cause crappy winter starts and rob you of power during the warmer months.
     
  4. 75-K5

    75-K5 3/4 ton status

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    But how could it find any warm air to direct right at startup? The exhaust manifolds are not warm before you start the engine, so the air you are getting immediately at startup is the same temp whether you have open element or the restrictive snorkel intake.
     
  5. 85scottsdale

    85scottsdale 1/2 ton status

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    But just after a few seconds of running those manifolds are plenty warm to provide warm enough air for the engine. I don't think having an open element would cause the idle to fluctuate like that though. Is it throwing any codes?
     
  6. B_to_C

    B_to_C 1/2 ton status Author

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    [ QUOTE ]
    Is it throwing any codes?

    [/ QUOTE ]

    ok so if i let it idle like this for about 3-4 minutes, the check engine light will come on. then go off, once i start drving. i only vaguely know about sticking a paper clip somewhere to get codes, but don't know how to do it. /forums/images/graemlins/1zhelp.gif
     
  7. bryguy00b

    bryguy00b 3/4 ton status

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    guess it could be that then since everyone is saying..but my first guess was actually TPS...cause my s-10 does that and its to do with the tps..
     
  8. elacruze

    elacruze 1/2 ton status

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    Sounds like a lean surge. You probably have an air leak. Check the gaskets around the spacer (you have one on both sides, right?) Check or have checked the idle air motor to see if it's gummed up and sticking. You still have all of your O2 sensors hooked up?
    Despite what someone else said, at first start it doesn't matter what's in front of your TB as long as it passes more air than the TB passes at idle. Your FI doesn't care whether the air's warm or cold, that only affects the emissions and fuel economy.

    Eric
     
  9. B_to_C

    B_to_C 1/2 ton status Author

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    thanks guys, i'll check the gaskets today...
     

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