Remotely mounting the ICM and ignition coil

[Chewy1576]

Has anyone had any experience and/or luck with moving the ICM from the distributor and the ignition coil from the mount next to the distributor and put them on the firewall, fender, etc? I think another ICM just burned up while I was out tuning.


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[Chewy1576]

One more question - if I install an MSD 6AL ignition box, would this replace function of the ICM so it could be removed completely, or does it still need to be there?


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[Supercharged111]

Negative on the MSD. What kind of ICMs are you using? The ICM helps control the ignition curve, so you need the correct GM I'M for your year truck, not just an L05. I say this because the LT1 in the Camaro calls for any 1 of 3 ICMs depending on the year and I know the L05 switched from ECM to PCM when it got the 4L60E.

 

[Chewy1576]

Negative on the MSD. What kind of ICMs are you using? The ICM helps control the ignition curve, so you need the correct GM I'M for your year truck, not just an L05. I say this because the LT1 in the Camaro calls for any 1 of 3 ICMs depending on the year and I know the L05 switched from ECM to PCM when it got the 4L60E.

I came to the same conclusion about the ICM after more searching. The one I suspect is shot is a BWD unit from O' Reilly. It was an emergency fix to get the truck home after breaking down and it has been running well since then so I didn't give it a second thought. I have a spare ICM that I'm going to swap in really quick and see if it will run again, but I don't know the brand.

I am no longer running the stock engine (now a 383). The PCM is a newer 16197427 from a '95 TBI truck that originally had a 350/4L80E, but I have since converted it to run TBI on the 383 with an NV4500. The distributor is new as of this summer (the pickup coil in the old distributor went out so I replaced the whole thing). The new distributor has an aluminum body, instead of steel. Could this be causing the ICM to overheat and fry itself?

I also have a big issue with the battery cables. The positive cable on the battery end had been cut/hacked in half at some point and pieced back together, and the negative terminal on battery is stripped out so there is a weak connection there too. I have also seen that bad grounding can kill an ICM pretty fast. I'm looking into larger custom battery cables as I type.

In my research about the MSD box, I came across some info about different models of the AC Delco ICM's. One will retard timing a few degrees above 4000 RPM, and another will add a few degrees of timing above 4000 RPM. If it does end up being a bad ICM, the next one will definitely be an AC Delco unit.

 

[Supercharged111]

Don't let an O Reilly parts failure sway your confidence in the truck. Lots of them go for multi-hundreds of thousands of miles before dying. They get a bad rap because they usually get replaced with junk. If you do have a custom tune and all that you can start with whatever AC Delco unit you want, but you'll need to stick with that exact part number because, as you've pointed out, some add/pull timing over 4000 RPM among other things. Don't forget to use that heatsink paste between the ICM and the distributor's mounting surface. That will definitely fry an ICM.

 

[Chewy1576]

Well as I suspected, the ICM was toast. The spare one I had was bad also I guess because the injectors would fire, but no spark. After a new BWD one from O'Reilly it fired right up. I guess I need to baby it until I can get those new battery cables ordered.