My 1990 Eagle Talon turbo AWD starts, runs about 2 seconds, then dies. It just started doing this when I took the ECM out from under the dash to look at the wiring. Sometimes by wiggling the wires around I can get it to run normally (not die). Then while it is running, if I wiggle the wires around where they go into the ECM, sooner or later the engine will die. When it dies, I first hear a relay click. The relay is just a few inches from where the ecm mounts under the dash. I think it is the ecm relay, but don't know. This same relay clicks whenever you turn the ignition key on or off.
I am really puzzled. It's acting sort of like there is an intermittent electrical connection somewhere, but it always starts! How could it start and run at all, even for 2 seconds, when the intermittent connection is bad? What is going on?

It sounds like your ECM may be bad. Check for reference voltages to select sensors, such as the MAP Sensor or Throttle Position Sensor. If you don't record close to 5 volts between the reference connector wire (+) and ground, with ignition turned to ON, your ECM is probably bad.

Reading sections A and B below should help and show you where I'm coming from:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-honda-civics-46563.html

I haven't checked reference voltages yet, but I pulled codes off the OBD1 port
Tonight with my voltmeter and it was perfect. Got steady pulses at about 1
Pulse per second which is supposed to mean that the ECM is normal and the
Sensors are good. Then when I turned the key off it kept pulsing for about
10 more seconds and then a relay clicked which shut the whole thing off. I
Did this 3 times, always the same result. I don't know how reliable a test
This is for telling whether the ECM is really all right or not, but it just
Looks to me like the wiring or connectors could be in poor shape.
The ignition #1 wire was previously hacked by somebody. Connectors 55 and 56 are actually pushed away a little bit from where they should be in the plug at the end of the harness. I see in my Chilton manual that #56 goes to the ECM relay, and #55 goes to the ignition power transistor. This caught my eye in the "A" read: "One relay is energized whenever the ignition is on, which supplies battery voltage to the ECM, power to the fuel injectors, and power for the second relay. The second relay is energized for 2 seconds when the ignition is switched on, and when the engine is running which supplies power to the fuel pump"
The check I did, reading pulses from the OBD1 port, is that a reliable way to know if the ECM is OK? Supposedly if the ECM is bad it will just put out a constant 12 volts, no pulsing.

. Replace hacked wiring.
. Test all under-dash and under-hood fuses with a multimeter.
. To me, it sounds like the ECM, or wiring, is interferring with the main relay working properly. If you have a MAP Sensor, check its reference voltage. It's likely the key sensor on your car, and, if it's not getting the proper voltage from the ECM, the main relay won't operate properly.