distributors and ICM (Page 1/3)
sledcaddie JAN 19, 02:04 PM
We all know that the Fiero ICM fails once in awhile. Mine on my 85 SE, with 100K miles went out last summer. Is this due to age, or many cycles of heat/cool? So, a new part, that has been sitting on a shelf for 25 years, wouldn't be affected? My main question is, for those of you who have replaced the complete distributor, have you had your ICM fail? What improvements do the (newer) replacement distributors have? Thanks for all responses.
steve308 JAN 19, 04:04 PM
New distributors are all "offshore" units but what isn't. They ICM that is included is generally equivalent to a second line lower quality unit. I recommend that if and when you replace the distributor you at least replace the ICM with a top line unit like a STANDARD Motor products RED BOX. Keep the removed ICM as a spare. When I did mine, I also replaced the cap and rotor with the SMP red box unit. You also might want to explore a heat sink for the distributor....just use the search feature.
Skybax JAN 19, 04:14 PM

quote
Originally posted by sledcaddie:
We all know that the Fiero ICM fails once in awhile. Mine on my 85 SE, with 100K miles went out last summer. Is this due to age, or many cycles of heat/cool?



All of the above, it lasted 36 years and 100k miles, can't ask for more than that. When I replaced the module in all 3 of my GT's they were all original and still working, I replaced them as preventative maintenance and kept the originals in the trunk as an emergency spare.


quote
Originally posted by sledcaddie:
My main question is, for those of you who have replaced the complete distributor....... What improvements do the (newer) replacement distributors have?



None, actually worse.


quote
Originally posted by sledcaddie:
So, a new part, that has been sitting on a shelf for 25 years, wouldn't be affected?



You will get different opinions, but I replaced hundreds of these on GM cars from this era, and IMO the best option is to buy a NOS module and quality pickup coil, replace them both at the same time, use a nice even thin coating of white thermal paste on bottom of module, and install onto a clean distributor surface with clean vent holes. This is the best prevention and should last another 36 years as long as your engine temps are normal and you have good ignition components (cap, rotor, wires, plugs, coil). The problem with modern aftermarket modules (even AC Delco) is they can't handle the heat. There is nothing wrong with using a module that has been sitting on a shelf since 1992.

Here are some part numbers for you to search for...

10482827 - GM alternate catalog
10496269 - 22P manual
Both point to D1943A as V6 replacement

D1960A is listed for the 86GT
D1943A is listed for the 85-87-88GT
Both work on V6

I've also seen all 3 of these scenarios:
#10496269 is on the box for D1960A
#10496269 is on the box for D1943A
#10496269 is on the box for D1992

Here is procedure from 2004 for replacement... https://www.fiero.nl/forum/...050410-2-057306.html

[This message has been edited by Skybax (edited 01-19-2022).]

css9450 JAN 19, 05:06 PM
I'd gladly use a genuine ignition module that was 25 years old and still new in the box. Probably a better item than the new ones.

Keep in mind though, the same D1943A is used in dozens of other vehicles, not just regular cars but lots of Chevy trucks. Probably all the 2.8 and 4.3 trucks. My old S-10 pickup probably used the same part number as my Fiero. Any new module you buy at the parts store is likely to be pretty fresh and new.
theogre JAN 19, 06:36 PM
Many miss that ICMs often die as a symptom of other problem like Iffy/bad spark plug(s) and other things on high volt side.

ICM mount screws are ground dirty or loose hardware can kill the module.
Worse only 1 screw is ICM ground for most GM distributors.

See my Cave, HE Ignition and Ground "Myth" notes

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

sledcaddie JAN 20, 03:06 PM
Thanks for all the info! I've never really heard of the pickup coil going bad, just the ICM.
sledcaddie JAN 25, 03:12 PM
Do you think it is possible that the 'heat sink' paste evaporates or dries out over time, so the heat doesn't dissipate as well, causing the ICM to get hot and fail?
Patrick JAN 25, 03:42 PM

quote
Originally posted by sledcaddie:

Do you think it is possible that the 'heat sink' paste evaporates or dries out over time, so the heat doesn't dissipate as well, causing the ICM to get hot and fail?



I've wondered that myself... although the thermal paste I used Here (along with mounting a heat sink) was applied 14 years ago, and still seems to be doing its job.
fierofool JAN 25, 06:36 PM

quote
Originally posted by sledcaddie:

Do you think it is possible that the 'heat sink' paste evaporates or dries out over time, so the heat doesn't dissipate as well, causing the ICM to get hot and fail?



I would think that if a heat sink paste is used that has high solids, even if the viscous carrier dried or evaporated, the solids would still transmit the heat away from the ICM.

As for the pickup coil, I've replaced three in different cars. One of them due to a failure. The other two were precautionary due to the degradation of the plastic on the harness end, and the sheathing that covers the coil itself.

theogre JAN 25, 07:42 PM
Most Heatsink Grease does dry out but still works after doing that.
The "oil" is just carrier to move the compound to install. "Oil" can be silicone oil or whatever liquid to make the stuff.

Don't go by fools in PC world saying you need re-grease or buy expensive crap. Worse some PC products are electrical conductive and "liquid metal" that hate aluminum.

That said...
I don't use HS grease anymore.
Use green label Permatex Brake Grease.
Will allow metal to metal hitting and fills tiny gaps to transfer heat. Plus unlike HS grease never dries or runs when hot.

Started this decades ago because Duke DIS ICM need something just to prevent "rusting" between ICM and mounting tray.
GM DIS ICM are too big and HS grease won't flow and cause stress to the ICM.
GM installs them dry but Dukes have low location and can get crap off of road stirred up by tires.

I use Brake Grease on PC CPU and more because is plastic safe if gets on PC parts. But it is True Grease so some Heatsinks can move after install.

[This message has been edited by theogre (edited 01-25-2022).]