I have a 85 Iroc with the 870 ecm when I plug my scan tool in it causes the idle to go and adds 10deg timing is there away to stop this, I am not going to switch to the 165 or 730 to get around this if someone has a simple solution it would be greatly appreciated.Thanks for all replys.

 

Scantools can read in a couple different modes depending on the scantoola nd the application. On the 870, Diacom can read in diagnostic and ALDL mode. One of those will try to set idle at 1000 RPM and do the advance like you mention. Just depends how you set the scan tool up.

On some of the DIY dataloggers, it is controlled by the value of the resistor that you use, I believe.

 

I am using a snapon scanner is there a way to get around this problem any help would be appreciated.

 

As far as I have read, no. The idle locking at 1k is how the system was set up to run when in ALDL mode and the only cure seems to be software.