I've been having this issue since I finally got the MS assembled in my factory 302 case. The problem is that my ECM terminals seem to be loose on the pins in the ECM connector. If I shift the ECM or wiring harness by so much as a 1/4", the engine runs like crap and/or stalls out and/or refuses to start. If I move the harness or ECM to a different position, the engine picks right up and runs properly.

I have already removed each and every terminal from the harness connector bodies and squeezed them as closed as I can get them to tighten them on the ECM pins. I'm in the process of doing so again. It doesn't seem to be just ONE wire, as I have held the ECM in my hand and wiggled each and every wire individually, while the engine was running, with no change. It seems to be ALL of them when shifted.

The question is: Is there any way to prevent this issue from happening again? Should I look into replacing each and every terminal on each and every wire in my ECM connector bodies? I can't go like this, with the engine running perfectly OK one day and running like crap the next because something seems to have shifted the harness in relation to my MSII ECM. I'm running a dash from a 93 Camaro and I don't have much room to work with in between the heater module and the glove compartment.

 

Jb weld. No im joking, lol, though it probably would work.

How do you have the ms wired in? Adaptor harness, MS harness, etc?

 

The MS is connected to my factory harness via a MS to GM 165 adapter board. Which is required due to needing the disconnect relay for the ignition bypass and also the relay for the coolant fan circuit. It's all in my stock ECM housing so it looks like factory (other than the blue ECM connector instead of black).

 

Ok, so its the ecm(blue) connector thats loose and not the db37 correct? If so, does the plug feel loose or is it just the pins inside the plug? If its the original plug, then the crimps that hold the pins together(where the plugs come together) are probably worn. Dont know how accurate that may be, but thats what I think may be going on.

You said you have crimped them to tighten them up i think, so most likely they are just worn and not holding the crimp well anymore.

Let me know if that makes sense to you.

Im also assuming you have cleaned all those contacts as well. If not try cleaning them with alcohol, worth a shot

 

The physical plastic plugs are tight. Almost TOO tight (they don't match the ECM connector in terms of the plastic keys that I had to cut off of them to get them in the ECM connector). It's the terminals in the harness connector bodies (on the end of each wire) that are moving.

The terminals seem to be pretty hard to come by. I have found ONE site with them for cheap (even Mouser wants whomever to buy a whole roll of, at a MINIMUM, 6000 terminals!). I'd need 36 of them to replace them all...

 

This may be worth a shot, I have done it before with success on loose terminals.

Try a slight bend on the male terminals, to try to maximize the tightness of the connection. I must warn you though, If you arent careful, there is a potential to break the terminals if you decide to attempt it.

The goal is to make the terminals slightly curved, but not enough to make the terminals weak, just gotta make sure they dont try to bend when you plug it in.

If you are successful, it may just solve your problem. But its ultimately up to you.

I think the other options would be to go JY hunting for a spare ECM and plug, or order those terminals and replace them. Unless you want to try cleaning the terminals with sandpaper or alcohol if they are oxidized.

Although now that I re-read the first post, you may just have to clean the terminals, sounds like a bad connection. I'd say clean them first and go from there.