1990 Delta 88 Check Engine Code 42 ?

Hello all,
I have a 1990 Delta 88 3.8 with 150k miles. Started having a problem
that I can't figure out. After I first crank it up the check eng light comes on.
Sometimes it comes on right away, sometimes after 10 miles or so. Most of the time I can turn the car off, crank it right back up and the light is off again until a few minutes later. When it comes on, the car will "stumble" a bit and the car loses a little power and the gas mileage drops. The power loss is the most noticable thing. I checked the engine code and it read 42 which
tells me this:

Electronic Spark Timing Circuit - Open or shorted to ground during engine run
or:
Direct Ingnition System fault - bypass circuit open or shorted to ground during engine run
or:
Fuel cutoff relay circuit - open or shorted to ground

Here is what I have done to try to fix:
New ECM
Changed plugs & Wires
Replaced the coil with another (used but good) coil

Now I'm stuck. Please let me know if there is anything else I can try.
Thank you!

Welcome to AF, most common cause of this code and related performance issue is the Ign contol module Napa and AZ can test them but it is not always accurate. Make sure all the pins in the connector at the icm are making good contact, this was another common problem.

I had this same problem with the car. Does it occasionally die on acceleration or refuse to start? I mean, VERY occasionally, sometimes going weeks without doing it?

Check the camshaft position sensor, and if the sensor is still good, then the magnet itself.

I had the cam shaft sensor replaced also but didn't fix it. I forgot to mention that in the first post. Never dies on acceleration. There was one time it completely died while driving but never did it again.

I think I found the problem. When I was inspecting the harness that goes in the ECM to make sure it had a good connection I started looking at the pins.
There is a rubber gromet/washer in there to keep moisture out. After closer
inspection I found that there were 2 washers in there. Apparently the pins weren't going in far enough to get a good connection. I've had to replace the ECM a couple of times over the years so it could have gotten in there when I changed it. Also my battery died so this could have contributed to the problem. Been 4 days so far and no Check Engine light on.
Thanks for the suggestions.