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I Need a lesson in Low-Temp Thermostats

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Lance, Jan 30, 2004.

  1. Lance

    Lance 1/2 ton status

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    A couple of members have offered up some advice on why my truck seems to be stumbling / starving for fuel at idle and when under load. (You can read about the whole sorted mess about the K5 in the "Bloody Knuckle" if you are so inclined.) Based upon the items that have been replaced (fuel filter, plugs, wires, cap, rotor button, MAP sensor) I was told that if I have a low-temp thermostat, this may be casuing me my problems. What I don't necessarily understand is why the low-temp thermostats would cause this reaction. I'm guessing it has something to do with timing advance or something similar but, I'm really lost. /forums/images/graemlins/1zhelp.gif
     
  2. rcpilot

    rcpilot 1/2 ton status

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    Looking at your profile, Your truck being a '90, they were designed, I beleive, to run in the neighborhood of 205-210, due to emmissions and stuff... if you are running a really low thermostat then it could be the temp is not up to where the computerr is programed for, thus causing erratic data for the system, also if you have vaccum ports they are most likely built to open a certain temps that you are now not reaching which could cause the vaccum system to also be erratic.
    Thats my take... I'm no GM mechanic but hopes this helps..
     
  3. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    If it runs too cool the system won't go into closed loop.
     
  4. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    A couple of members have offered up some advice on why my truck seems to be stumbling / starving for fuel at idle and when under load. (You can read about the whole sorted mess about the K5 in the "Bloody Knuckle" if you are so inclined.) Based upon the items that have been replaced (fuel filter, plugs, wires, cap, rotor button, MAP sensor) I was told that if I have a low-temp thermostat, this may be casuing me my problems. What I don't necessarily understand is why the low-temp thermostats would cause this reaction. I'm guessing it has something to do with timing advance or something similar but, I'm really lost. /forums/images/graemlins/1zhelp.gif

    [/ QUOTE ]

    Check my reply today on your original post.
    I explained why /forums/images/graemlins/thumb.gif
     
  5. bablazer73

    bablazer73 1/2 ton status

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    rif hit it.
    [ QUOTE ]
    If it runs too cool the system won't go into closed loop.


    [/ QUOTE ]
    Aftermarkey computer proms want you to run a lower T-stat, But the prom will accept that. Stock EFI won't.
     
  6. 4xcrazy

    4xcrazy 3/4 ton status

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    Too low of a t-stat keeps the engine in "cold mode" or as others are saying Closed loop. It basically tells the computer it still cold and in turn is giving the engine more fuel. This does work however on sports cars, i had an Iroc i did this to, used a 180 t-stat and lower temp fan switch, it ran faster, but in turn, used more fuel. As far as starving/stumbling, how many miles are on it, if near or over 100k and never changed the fuel pump, it may be losing pressure, i had this happen to my 89 Burb, same type of stumbling just no power at all, but idled fine. 100k is about the average life of a stock electric in tank fuel pump. Check fuel pressure and always run the recommended t-stat for computer controlled engines unless looking to use more fuel for more power. Just my .02 cents

    T.J. 4xcrazy
     
  7. Lance

    Lance 1/2 ton status

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    Thanks for all the input everyone. That's basically what I figured.

    As for the problem, it was in the fuel pump / strainer. Replaced them both and it ran perfect.
     

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