With the EST wire disconnected the module in the distributor will advance the timing BY ITSELF in a jump of about 16 degrees as you are describing. This happens when the rpm gets over 600 or so. It just jumps.

This makes setting the base timing with a cold engine very hard to do because when the engine is cold it wont run well below 600.

 

There's a timing advanced hooked up to it somewhere. Disconnect it and you're on the way to freedom

 

Here's a copy of the schematic. If you unhooked the EST connector (TAN-BLK wire), then the distributor has to be changing the timing dynamically on it's own (either through malfunction or otherwise). I see no inputs other than from the Pick-Up Coil itself. I'd not previously heard that this distributor will advance timing when RPM >600, but this may very well be so.

 

I understand that the timing advance within the module is not common knowlege but it should be.

Its a shame that it isnt mentioned in the how to set your timing articles or in any of the manuals but rest assured, the timing will change with the est wire disconnected.

 

88305tpiT/A is right, the dissy will automatically add ~20 degrees of timing at 2000 rpm, this is a "backup" incase somthing goes wrong with the ecm.

When you say the timing fluctuates, is this with the EST connector unhooked? Once the est connector is hooked up your timing is going to fluctuate a good bit with that lumpy cam. Motors with cam's won't idle with real low timing like a stock motor will. Set your timing to 4 deg with the est unhooked and forget it, once your plug the est back in you'll have way over 20 deg.

I think your problem has more to do with your untuned ecm. I know you payed good money for that chip, but there is no way that some one 1000's of miles away is going to be able to burn you a chip that will run your car perfectly on the first try. I bet the car will run much better once you get it up to operating temperature and into closed loop. GM ecm's actually have quite a bit of self compensation built in. If it does run better once warmed up, I would deffinately suspect the tune.

 

I have a question about testing the external coil in the pic way up there (same as chilton) on step 3 it checks for open says put on high scale should not read infinite, but does anyone have what the correct range it is supposed to be? I suspect my coil is going out and it doesn't read open on step 3 but it reads 9.5K ohm when hot and i think I tested it cold once and was a little lower @ 8.5K ohm or something. I was gonna see if parts store might let me test one but figured I'd see if someone with a STOCK external coil could give me the value of theirs..


EDIT: well I did get them to let me test a new one at part store and it ohms out about the same 9.2K ohm.