870 Spark Control

[Programmer]

Can you give me a little history here--is this a modded unit, or totally factory. Can you upload your bin to me ?

Lyndon.
  ----- Original Message ----- 
  From: Matt Sandine 
  To: gmecm at diy-efi.org 
  Sent: Friday, May 11, 2001 1:46 PM
  Subject: Re: 870 Spark Control


  I am not kidding. It bucks and sputters all over the place, but that is what is really happening. You can tell the fuel is totally being ignited at the wrong time. I thought my timing light could be way outta wack. I used another with the same results. She purrs like a kitten when the timing connector is disconnected and it is at 6 deg, besides the fact that you can't rev it because the computer isn't adding the spark. Just in case the balancer was slipping, I marked the pulley. It is honestly retarding the spark at least 20 degrees from the 6.
  Does this make sense? The only way I have been able to figure out spark advance on the 85 (since it doesn't show it in scan tools) besides using a timing light is to use a scope on the pickup coil input and EST output at the computer harness. By tracking both of these waves at the same time, I was able to see the EST get tighter and tighter compared to the pickup coil pulse remaining constant. Only problem is, I need to try to figure out if the EST pulse is actually being retarded from the computer or if it is being retarded at the ESC module. Thanks for the interest Lyndon, -Matt-

     
    Matt,

    If this thing was going into 24 degrees retard from 6 BTDC, it'd stall. Are you 100% sure it's going 24 ATDC ?

    Lyndon.

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