idle surge when coasting at low speeds

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  • Jewelnohio
    • Apr 2004
    • 11

    #1

    idle surge when coasting at low speeds

    92 Cutlass Supreme 3.4 dohc . engine 199k miles xmission 100k miles. Engine starts and idles fine .Runs at highway speed ok . Shows egr code when letting off gas at highway speeds but has done that for 5 or 6 years and never had any problems before . When driving at low speed around 25 mph and let off gas , idle surges up and down approx. 1000 rpm for 3 or 4 times then returns to normal . Doesn`t do this all the time . Any ideas what is causing this ? Thanks for any Help
  • Doubt_Incarnate
    I still watch ROBOTECH!
    • Jan 2005
    • 1130

    #2
    maybe your egr has a leak to the outside air.
    If you aren't friends with a liar, you aren't friends with anyone.

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    • Syn
      The Master Piece
      • Oct 2005
      • 599

      #3
      yeah possible vaccum leak
      sigpic

      1993 Cavalier Z24, 3.1/3400 hybrid, crane 272 cam, LS6 springs,port and polish,2.5 exhaust to 80 series flowmaster,solid mounts

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      • z34phoenix
        • Jun 2005
        • 469

        #4
        yeah if the egr is leaking or failing it will mess with it.... but that much of a shift in RPM makes me think intake leak... maybe thru the EGR Like said above.

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