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88 k5 intermittent code 42..Help!

Discussion in 'The Garage' started by one, Apr 4, 2004.

  1. one

    one Registered Member

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    Ok...just recently my k5 has started surging at idle from around 800 down to 500 and every once in a while stalls and sets a code 42(est circuit problem). So I replaced rotor, cap, wires and the ignition module, checked to make sure prom is seated correctly and checked all est wires for opens or shorts...nothing. Vacuum is good, no leaks. Is there anyting else that can cause a code 42 to show up? I really don't want to just start throwing parts at it.(has new egr and egr solenoid) I'm wondering if it could be the iac valve but it didn't throw that code...Help!
    Ben
     
  2. MudFrog

    MudFrog 1/2 ton status

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    I think it was a code 42 when my knock sensor went out. Can't remember 100% sure. But you might want to look into it.
     
  3. 4xcrazy

    4xcrazy 3/4 ton status

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    I was reading that the code 42 is for the electronic spark control module... Didn't replace that, did you, it's pricey too, i did. Like $75 or so

    Check this out and see if it helps out any,,,
    web page
     
  4. shaun

    shaun 1/2 ton status

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    I had the same problem for a while. Finally I rebuilt my tbi, replaced my IAC, TPs and a vaccuum hose and It went away. My knock sensor wasnt affected. But that was just me. /forums/images/graemlins/waytogo.gif
     
  5. one

    one Registered Member

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    thanks for the tips...I just replaced the iac valve(was looking kind of out of whack anyway) but it did'nt help the idle at all...I'm wondering if I can just disconnect the knock sensor and run the engine to see if it idles differently. wish me luck...
     
  6. shaun

    shaun 1/2 ton status

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    Just disconnect the quick disconnect for doing your timing (brown i believe) And have someone watch your timing while you hit your block with a wrench or metal tube. The timing should retard itself and go back. /forums/images/graemlins/waytogo.gif
     
  7. Thunder

    Thunder 3/4 ton status

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    Its prolly your magnetic pick up coil. They set a 42 when they go bad. They can also cause missing and stalling.
    Dist module(ESC), pickup coil, and bad ground/wireing can set a 42
    Knock sensor/Timing module(ETC) will set a 43 so I doubt that is your problem.

    You have to pull the dist to change the pick up coil.
     
  8. one

    one Registered Member

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    thanks for the tips again...knock sensor is ok...replaced dist. (it was corroded inside and the wires to ignition module were cracked and about to fall off) weirdest thing though, no more code 42 but it's still stalling at idle when warm(????)...so I thought I'd check the fuel system...injectors are throwing a very uneven pattern with droplets just dropping off the tips...how long should injectors last? I'm coming up on 130,000 on the k5.
    Thanks again
     
  9. Thunder

    Thunder 3/4 ton status

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    Sometimes when you look at the injectors at idle it just looks like drops are coming out. The best way to check them is to hook up a timing light and shine it on the injector. That will catch the true shape of the pattern.

    Hows the base gasket on the TB If it is leaking it will cause idle problems.
     

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