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What do I need to replace?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by heavy4x4, Sep 22, 2003.

  1. heavy4x4

    heavy4x4 1/2 ton status

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    Location:
    Delafield, Wisconsin
    My truck has, for the last couple of months or so, developed a varying idle. Both when the truck is cold and at operating temps, my idle will go from ~800 then lug down to ~600 or so, and then pick back up.
    I've replaced the O2 sensor and TPS in the last 3 months and spark plugs, wires, and engine temperature sensor in the last year and a half. I've got an el-cheapo (Wells) distributor cap and rotor sitting in the garage, but I'm debating whether or not I want to put that on.
    So, what should I replace now in hopes of getting a steady idle? I'm almost sure you're going to say replace the IAC, so if that's the case, where should I get one...should I just get the generic parts-store replacement? What about the EGR? (it seems to work alright). MAPP? -Should I just keep on listing all the sensors? /forums/images/graemlins/rotfl.gif Also, do you think I should replace my coil. As far as I know (I can check if need be by looking at receipts), the same coil has been on there for over 100,000 miles.

    Thanks for your input. /forums/images/graemlins/thumb.gif
     
  2. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    IAC. This might happen if the IAC can't make slight movements in the area between 600-800RPM. I bought my last IAC for $35 IIRC @ AutoZone. Works fine for me...

    -Dan
     
  3. jpaitala

    jpaitala Registered Member

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    Could be the MAP-sensor also. I had to replace it in order to get the idle back to normal.
     
  4. R72K5

    R72K5 Banned

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    at least remove the IAC motor and use carb cleaner and clean it off good and the hole in the TBI unit for it and blast out with compressed air and reinstalla nd see how it does then, this is soemthing that needs ot be done now and then anyways but no one does, the tip of the IAC carbons up and the IAC cant adjust very well and will mess up idle big time

    also on a TBI engine i found out that a big cause of bad cold running engine is bad distributor cap, center post arcs allw ay around and center wire post cracks all way around, but will run pretyt good warm though, i dont know how, we had this happen to a 92 4.3L gmc c1500 pickup out here recently, the cap was arced super bad and it ran like junk when cold til it was warmed up, i cleaned IAC off and it didnt help much that time, but it usually does on a TBI engine that isnt running right.


    i found out another problem on TBI engines is the pink hot wire from coil on the intake over to the distributor, it breaks up inside the insulation and you cannot tell, and will cause engine to die for no reason at all, but will restart if you mess around with the wire at near the coil pack end.


    30 dollar wire at GM counter. could not figreout forever why it would die and not restart for a while ornot at all or sometimes right back up, basically whenever it felt like starting up,

    what happens is that when coil doesnt get juice then the TBI wont fire injectors either.

    so if you have one not start for you then check for spark and check for fuel spray, if both are gone then its hot to primary of coil pack IE wire busted inside insulation,


    found out the hard way.......

    the white smaller wire right next to it was fine
     

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