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Retarded ignition??

Discussion in 'Chevy C/K Truck Forum' started by Boreal, Mar 17, 2009.

  1. Boreal

    Boreal New Member

    I have hooked up a ScanGage to my truck and the Ignition timing ranges from -15 to -24. Does this mean ATDC? Would this be a normal reading for a truck with an ECU? My old 85 used to be set slightly advanced at idle and would increase under acceleration.
  2. mjalstad

    mjalstad Rockstar 100 Posts

    I used to have a Grand Prix GTP and I was really into tuning. I think the 98 Grand prixs always read negative numbers for timing, so maybe yours is the same way. Your timing should decrease under acceleration or heavier loads and be high when cruising. My timing goes all the way up to around 50.
  3. Boreal

    Boreal New Member

    Thanks for the info. Another question - is a reading of -28 equivalent to -28 degrees ATDC with a timing light?


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