My D150 was built mid 85, sold as one of the first 86 ECM in the fender trucks. At some point had the same issue y’all are experiencing, but in the form of hesitations at light throttle at speed with light/medium throttle loads being a firm labored misfire. I believe my grandfather mechanic at some point did the ignition back dating to delete the ECM from the equation as described. Runs decent enough to drive, but lacks drivability unless you ease/roll in and out of throttle. In combination with other intricacies of maintenance, my trouble shootings a little more complicated. None the less these pages from my 86 FSM might help some folks.

 

 

 

 

 

hopefully they all uploaded clearly and in order. If there are any other pages you need, let me know and I’ll try to post them. Eventually I’ll scan the whole book to PDF and share it with the admins to sticky.

 

Here’s a few pictures of my ECU part number as a possible reference. As well as an engine bay layout? Picture for comparison of component placement. (The zip tied resistor wasn’t my doing and is on the fix it list.)