Yes, I meant discharging the capacitor in the ECM that erases the keep alive memory. A few things come to mind, heat being one of them, the other being that of open loop and going into closed loop operation. Although that would not cause a loss of spark, if you're positive that it's the actual problem.
I mention heat because if the ECM is over advancing timing due to base timing being off, you could try unplugging the spout connector and see if it still stalls out. I know you'll be running at base timing, which is only 5 to 10 degrees, but this being obd1 getting any live data pids is impossible.
The check engine light coming on or not during the fault will indicate if the ECM is possibly losing power or not. And the Tach jumping while cranking will tell you if there is any signal from the pickups in the distributor.
This is all tied together, but I'm assuming you may be losing coil control, which you can check with a test light hooked to battery positive and touch on the negative side of the coil while cranking, and should have a dim flash on your test light.
If you have nothing but 12 volts on both sides of the coil, then there is no control. It's odd having to erase the memory on the ECM though, that's not really a good thing to be doing, the ECM is losing all its fuel trim memory from that.
With the key off check the ECM connectors for any corrosion inside the connector pins, or any main bulk connectors for corrosion. That would be a concern if pins are shorting out either to power or to ground. Possibly spiking the ECM. Another thing to check would be the underside of any fuse/relay panels in the engine compartment. Look for the common white or green crusty corrosion.
I know the ICMs tested okay at the auto parts store, but these things are known for multiple failures and are so common. If you have more than one, maybe try swapping one out after the stall before doing the cap discharge. Just to really verify what's happening here. And before possibly replacing the ECM, we should load test the power and grounds to the ECM with a bulb that can carry some current. With the ECM unplugged, there could be a harness issue anywhere with a vehicle this old, and check that the distributor shaft doesn't have any play in it.
Sorry for the list of a million things to check and a lot to think about, but it's better to be sure before spending anymore money on parts.
Monday, November 7th, 2022 AT 3:58 PM