Dielectric grease is the wrong thing to use in that application! You need thermal paste! It assists with heat transfer to the heat sink! Dielectric grease that may have come with it is for the connector. Not sure why they don’t come with thermal paste…

 

You are correct - I misspoke. I used thermal, not dialectric. I'm having all kinds of cognitive issues this morning. Need more coffee.

 

You’re good, we all have those days. Just wanted to make sure! I learned the hard way on that lesson.

 

Quick update: I spent most of today digging through the wiring and found quite a bit wrong. Once I started opening up the harness it was clear there had been a lot of previous repairs, and some of the wiring was in really rough shape. I found multiple sections with melted insulation and poorly done splices.

I ended up rewiring the circuits from the distributor back to the ECM, and also repaired the wiring block under the fuse box. While diagnosing things, I checked resistance from the ICM ground to chassis ground and was reading about 30 ohms, which is obviously far too high for a proper ground path. Because of that I kept tracing the wiring and repairing sections as I found them.

I also went through both transmission harnesses and rewired them. Those were an absolute disaster — in some spots the wiring wasn’t even properly connected and the wires were literally just twisted together.

In addition to that, I rewired the ignition coil harness as well. The noise you hear in the YouTube video I posted earlier is actually the ignition coil firing.

I also tested the ICM following the specific write-up I referenced earlier in the thread and it checked out according to those procedures. After repairing all of the wiring, the engine definitely runs a lot better overall. However, once the engine reaches operating temperature it still starts exhibiting the same issue as before.

At this point I’m starting to suspect the ECM may be failing, possibly heat-related. Has anyone seen an ECM start to malfunction only once it gets up to temperature, or is there another circuit or sensor I should be checking before condemning the ECM?

 

That can and does happen at times with an ECM. Taking a look at it can’t hurt!

 

I pulled the ECM and it looks like it has seen better days I sent the ECM to ECU exchange to see if they can fix it before buying a new one hopefully this puts an end to this mystery some of the capacitors look pretty burnt out

 

Should be pretty easy to redo. May have to fix a trace on that last picture.

 

Fingers crossed the problem was the ECM. As stated in the email the tech found a couple things wrong so hopefully I get it back soon to put it into the truck and see if it acts right!