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350 TBI no fast idle

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by tch777, Jan 15, 2003.

  1. tch777

    tch777 1/2 ton status

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    Hi all new member alert.
    My first question of many to come.
    The fast idle doesn't kick in when we start the /forums/images/graemlins/burb.gif in the morning, where should I look. I just did all the sensors this summer except the TPS. The injectors are original with 123,000 miles.

    Thanks

    Tim
     
  2. heavy4x4

    heavy4x4 1/2 ton status

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    Ok, let me throw out some ideas here:

    You said you did all the sensors except TPS, so am I correct in assuming that you replaced the coolant temp sensor on the front of the intake manifold? If not, that's the first place I'd look. What's happening at cold idle is that the computer gets some information that the engine is still cold....so it dumps more fuel in, thus raising the engine rpms and temp. If that sensor has been replaced/is good, check the connections at the very least (when the engine is going and warm, disconnect it, you should hear the rpms increase.) Based on your description, I'd say the coolant temp sensor is the culprit.
    Ok, next suggestion...there is an idle air controller (IAC) located at the base of the TBI unit at about 10 o'clock when looking down on the unit from the front of the engine. It's an electrical fitting, so check those connections too.
    Finally, another sensor...but as a last resort, check the O2 sensor. I don't see how that could be it, but maybe (you know how those "wonderful" computers work /forums/images/graemlins/smirk.gif)

    By the way....welcome aboard!!!! /forums/images/graemlins/thumb.gif If you'd be so kind, go to "My Home" and go to the edit area and fill out your profile. That's so we can see who you are, where you're located, and what you drive. /forums/images/graemlins/thumb.gif
     
  3. tch777

    tch777 1/2 ton status

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    Thanks Heavy,

    I am pretty sure I replaced the temp sensor but I will check it out. I did the O2 sensor but will check it too. I will check the IAC as well. Do you have any snow?

    I am from Chippewa Falls, WI. My folks say no snow but cold.

    Thanks

    Tim
     
  4. heavy4x4

    heavy4x4 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    no snow but cold

    [/ QUOTE ]
    Exactly that!!! Not a bit of accumulation on the ground right now, but it's been hovering around 20 degrees for the last week (with a stiff wind too). Don't get me wrong, I love winter....but if it's going to be this freaking cold, I want FEET of snow on the ground. /forums/images/graemlins/smirk.gif /forums/images/graemlins/angryfire.gif
     
  5. 87sm465np208

    87sm465np208 1/2 ton status

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    its the idle air control, mine did that in summer thank god, but that is what happend on mine, when it got slightly colder out, it didnt idle at all. good luck.


    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/truck.gif
     

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