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91 k5 ignition woes.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MR4WD, Feb 12, 2003.

  1. MR4WD

    MR4WD 1/2 ton status

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    Location:
    Fort McMurray, Alberta.
    When the truck is first started, and the engine ambient temperature is below (freezing) it runs like a top. As it heats up, and approaches running temperature it will lose low end torque and seemingly backfire through the carb. In my opinion, it also seems to ping, but very lightly. It's a 350 hooked to a 465, running 3.08's with the dinky 235's... So, even at best this engine never really sees much RPM... But while going up a hill, I can't do it in 4th without the motor lugging and pinging... I've got to wind out 2nd gear just to be able to grab 3rd without the motor lugging...

    I adjusted the timing to stock specs (while unplugging the computer advance as per required, and the engine's definitely not starving for air)

    Being TBI, I'm mostly scared to get start adjusting this and screwing with that like I would with carbed engines... I haven't pulled the distributor yet, but I'm thinking that it may have too much end-play and it could require new bushings. The timing chain may be worn, as I'm approaching 180,000 with the stock engine but I doubt it...

    Anybody have any ideas, or areas that I could trouble shoot? Any help would be appreciated, thanks.

    Chad.
     
  2. GRINCH

    GRINCH 1/2 ton status

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    Check your coolant sensor... The one on the manifold not the block. I have the specs at home for resistance to temp.
    I'm at work now so if no one posts them I will when I get home.
     
  3. MR4WD

    MR4WD 1/2 ton status

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    Sounds like something I could look into. I don't own a manual for this truck either, which is something else I should probably look into... Either way, what's the procedure for that? I'm pretty adept at mechanical parts, like setting up diffs, rebuilding engines and building trannies, but when it comes to stereos and electronic engines I get scared... Thanks for the help..
     
  4. Thunder

    Thunder 3/4 ton status

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    Coolant temp sensor is a good place to start.
    You should learn to check for trouble codes also. many times the computer will tell you whats wrong.
    Heres how to and what the codes mean: GM trouble codes
    (Your data link is under the steering wheel on the bottom of the dash.)
    It helps to have a good manual too.
     
  5. Blazer1970

    Blazer1970 1/2 ton status

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    What do the plugs look like after it has been running warmed up for a while. From the symptoms, it sounds like it is running lean. You don't notice it during warm-up mode, since the computer richens the mixture until the CTS shows the engine is up to temp. Is the idle air control (IAC) on the throttle body stuck open?
     

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