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whats the problem?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by therover87, Jun 24, 2001.

  1. therover87

    therover87 1/2 ton status

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    i have an 87 k5 and i replaced the wires with msd 8.5mm, i have the msd hei coil, the cap and rotor, i have ac delco rapidfire spark plugs but for some reason my truck is running very rough at idle and it seems like there is a lack of power, there is a backfire through my exhaust as well any help would be appreciated
     
  2. KrebsATM02

    KrebsATM02 1/2 ton status

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    have you timed your engine lately?

    Doug Krebs
     
  3. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Sounds like a wire got cross over with another one.

    Also, were the coil wires the same color when you took the old one out and put in the new one? If I remember right, there is a yellow, red, and white wire but certain years only use two of the colors and other years use the other color.

    <font color=red>I m so we Todd did.
    I m sofa king we Todd did.</font color=red>
     
  4. txbartman

    txbartman 1/2 ton status

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    I agree with the timing issue. When you accelerate, does it seem to significantly hesitate before it responds? If so, combined with your other problems, I would say you are firing late.

    85 GMC Jimmy, 305 w/TH700-NP208, 32X11.5 BFG ATs, 15x10 Eagles, Smittybuilt tube nerf bars and bumbers
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'm with Westy on this one, I think you got a couple of wires crossed.

    Rene


    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  6. Pugsley

    Pugsley 1/2 ton status

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    I concur - check the wires

    I'm so poor I can't even pay attention [​IMG]
    <A target="_blank" HREF=http://pugsley.alloffroad.com>http://pugsley.alloffroad.com</A>
     
  7. shawnboy

    shawnboy 1/2 ton status

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    Like the other fellas said, check to see if your wires were r&r'd properly. But just as important is your spark plug gap. Stock .035 works ok for stock ignitions but when you run that MSD you have to set your gap at least to .045-.050 to run cooler. Very important.
    Shawnboy.
     
  8. Highlander

    Highlander 1/2 ton status

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    Have you looked for vacum leaks yet? That and timing ,wires Are things i'd look at.
    Have Fun Cethern

    Lost? i'm not lost i'm just disorienated
     
  9. therover87

    therover87 1/2 ton status

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    i am not sure cause this problem just started and i have had the wires on for about 3 months
     
  10. therover87

    therover87 1/2 ton status

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    i am not sure cause this problem just started and i have had the wires on for about 3 months
     
  11. Wheels

    Wheels 1/2 ton status

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    One other thing to check is the length of your spark plugs (threaded portion). Older Chevys used the shorter reach (.460) and newer chevys (86 on I believe) used the longer reach (.750). This is important to get the plug tip into the combustion chamber. If they are too short, they will not fire the cylinder properly and foul out real quick (they won't get hot enough to burn off the fouling). Just a thought.
     
  12. slider79blazer

    slider79blazer 1/2 ton status

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    you say it just started and had the wires on for three months you might have a wire that rubbed or is shorting out on something. also "rough at idle" is that in drive or park. if it is in drive I would look for a vacuum leak. hope this helps. good luck

    whats a 4 letter word for farm wagon? (ford) [​IMG]
     

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