bad idle and shuts off
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Northstar Engines and System Technical Discussion Discussion, bad idle and shuts off in Cadillac Engine Technical Discussion; just adjusted the ISC motor i have a question , when i adjusted the gap and reconnected the ISC motor ...
  1. #1
    tuka is offline Cadillac Owners Member
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    bad idle and shuts off

    just adjusted the ISC motor i have a question , when i adjusted the gap and reconnected the ISC motor , the plunger still hits the throttle plate , is that normal? idle jumps to about 500 and lower sometimes it shuts off the car in cold weather, the egr is cleaned , could it be carbon chunks somewhere in the egr valve passage?
    car is a 1994 STS northstar

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: bad idle and shuts off

    The plunger should touch the throttle when it is idling. There should be a gap when the engine is off. How did you adjust it?

  4. #3
    tuka is offline Cadillac Owners Member
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    Re: bad idle and shuts off

    Quote Originally Posted by Ranger View Post
    The plunger should touch the throttle when it is idling. There should be a gap when the engine is off. How did you adjust it?
    i followed instructions from here , hold rpm and push plunger to retract at the same time i disconnected the motor cable , then the car stalled on me though , im not sure that was supposed to happen but i continued adjusting the gap with engine off . when i adjusted the gap i reconnected the cable

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: bad idle and shuts off

    Sounds like you made the adjustment correctly. Now WHY did you adjust it in the first place? When is the last time the TB was cleaned? Have you checked for vacuum leaks?

  6. #5
    tuka is offline Cadillac Owners Member
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    Re: bad idle and shuts off

    because of the bad idle and car shuts off, should i just screw the plunger back while the car is off more? i will check for leaks . also TB is clean , no codes on the car either
    edit : the ISC motor is also replaced with a new one

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: bad idle and shuts off

    OK, you retracted the plunger, it bottomed out and then you pulled power, right? What gap did you set?

  8. #7
    tuka is offline Cadillac Owners Member
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    Re: bad idle and shuts off

    yes i left a gap about the thickness of a credit card, then plugged the power back in and started the car

  9. #8
    tuka is offline Cadillac Owners Member
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    Re: bad idle and shuts off

    i forgot to mention one of the mufflers is toast , 2 big holes in it , read somewhere on youtube guys 94 sts was stalling because of bad muffler?

  10. #9
    Ranger's Avatar
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    Re: bad idle and shuts off

    That doesn't even sound logical.

    You might check the EGR again.

  11. #10
    tuka is offline Cadillac Owners Member
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    Re: bad idle and shuts off

    ok i took the egr off , with the cable still on it , cycled the ignition and watched for movement in the EGR , the pintle did not move , im guessing it is broken?

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    Submariner409 is offline If it won't run, chrome it
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    Re: bad idle and shuts off

    EGR only operates with the engine running at light to moderate loads; it does not operate with the engine off or at idle.

    You could test the valve by removing it and applying 3 to 5 VDC across the terminals - it receives a varying voltage according to a PCM signal - matter of fact it may not operate until the emissions systems go open loop at 160 degrees coolant temp.

  13. #12
    drewsdeville is offline Cadillac Owners Master
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    Re: bad idle and shuts off

    ^^^yeah that. Perhaps a more convenient method would be to use the override feature (function PS02 for EGR) in the onboard diagnostics to manually command the EGR as you please.

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