Well, I bought a 87 Iroc recently with a know idle problem. She allways run very very good , but when I stop in a light allways stall. Any times the idle is good, but only in P (automatic), when put any gear engine stall.

I check with the scan tool and I find that the timing is set at about 27-29º at idle, first dont take a lot of value to this, but when I check the timing advance in my other 91TA, I see the advance at idle set at 16º.

Then I check the advance with the timing light and the check wire disconected in the Iroc, and it is where it must be, at 6º, and advanced untill 14º the engine never stall, even with gear, lights, fan..... After set again at initial 6º and Checked with the timing light and the wire reconected it is nearly 30º.

Conclusion: The problem is reduced to the timing advance system.
-The electronic spark timing (EST) is good. I also prove the EST from the TA and the problem persist.
-The distributor advance work properly, as the timing advance gain about another 18º when I raise the revolutions, until about 44º total at 3200 rpm.

Now my dudes is reduced to a pair of components, and now is when I need the opinion of any ignition guru

I doubt about the electronic spark control (ESC) or the knock sensor.
What do you think about?

Here there are not any more cars to swap these sensors and prove

Thanks for your opinions. Fran