I will go out on a limb here. I have previously stopped giving advice via the internet since someone got mad when I diagnosed his problem as being a timing chain despite his assurances that it was perfect. Turned out it was the problem.
Now back to your problem.
Run a ground wire from any place to the mounting bolts of the ECU. The ECUs MUST be grounded to properly function and will give you all kinds of insanity to figure it out. I always go from the hood hinge bolt back to the mounting bracket where the ECU bolts to the bracket.
This may not fix the problem but it can't hurt.
One thing I learned from my grandfather (I wish I had listened more now) was that, "You electrical connection is only as good as your ground." Good Luck.
Kevin