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As the title says. What is it with new icm's ? I'm about to purchase my 3rd in 2 years. My 35 yr old factory one however is still fine. Only reason I ever replaced it was because the distributor was a rusted heap of crap so when buying a new one I thought why not replace the module too.
They've all been ac delco and all just randomly die. (Yes I used the heat sink paste on them) Car worked fine yesterday came out this morning and just cranks and cranks and nothing so being reminiscent of the last time it failed I decide to swap in the old one and it fires up.
Aside from hoarding a trunk full of back up icm's what am I/we to do ?
Does it happen to anyone else ?
How can you ever trust the car if parts as important to its functioning as the icm just die in a matter of months without warning ?
It's enough to make me sell the car.
Mystery eh?
I swapped my OEM one for the one that was included with JEGS #555-40006 distributor. I wanted to do some testing with tuning. I was getting erratic rpm at WOT engine load (https://www.thirdgen.org/forums/dfi-...ting-high.html)
The new ICM was behaving exactly like the OEM one. I left it there. It has been 2 years.
I kept my original one as I am excepting this "not USA made" ICM to expire soon... sadly.
Which is the correct icm for a stock 1988 305 TPI?
I don't recall there being 2 different ac delco ones last time I ordered, maybe I've ordered incorrectly ?? Don't know if that would cause them to die quicker or not.
Which is the correct icm for a stock 1988 305 TPI?
I don't recall there being 2 different ac delco ones last time I ordered, maybe I've ordered incorrectly ?? Don't know if that would cause them to die quicker or not.
I would go with the D1984A, seems like the other is for TBI…it seems a lot of aftermarket replacement parts are junk, especially electrical. It used to be the only good ICMs were AC Delco or GM.
Like DaveyDug mentioned have you tried the NOS Route on eBay? More of a proven commodity at this point.
As the title says. What is it with new icm's ? I'm about to purchase my 3rd in 2 years. My 35 yr old factory one however is still fine. Only reason I ever replaced it was because the distributor was a rusted heap of crap so when buying a new one I thought why not replace the module too.
They've all been ac delco and all just randomly die. (Yes I used the heat sink paste on them) Car worked fine yesterday came out this morning and just cranks and cranks and nothing so being reminiscent of the last time it failed I decide to swap in the old one and it fires up.
Aside from hoarding a trunk full of back up icm's what am I/we to do ?
Does it happen to anyone else ?
How can you ever trust the car if parts as important to its functioning as the icm just die in a matter of months without warning ?
It's enough to make me sell the car.
Indeed it is a head scratcher. After going through one every few months for over a year I finally went back to NOS AC-Delco units and called it a day. However, for extra insurance I bought one of these:
and bolted it to the underside of my distributor. I used extra long screws with the same thread pattern as the original ICM screws and then just put some backing nuts underneath.
That was 2 years ago and (fingers crossed) I haven't replaced it since. Which is the longest I've gone on an ICM since about 2016.
I would go with the D1984A, seems like the other is for TBI…it seems a lot of aftermarket replacement parts are junk, especially electrical. It used to be the only good ICMs were AC Delco or GM.
Like DaveyDug mentioned have you tried the NOS Route on eBay? More of a proven commodity at this point.
I didn't even notice the tbi 🤦♂️ I was just looking at the pics and part numbers!
I haven't been able to find any listing, could be a geographical thing on ebay since I'm in Australia but even choosing worldwide listings I still get no results.
Indeed it is a head scratcher. After going through one every few months for over a year I finally went back to NOS AC-Delco units and called it a day. However, for extra insurance I bought one of these: https://www.amazon.com/Genuine-Parts.../dp/B0012P2EQU and bolted it to the underside of my distributor. I used extra long screws with the same thread pattern as the original ICM screws and then just put some backing nuts underneath.
That was 2 years ago and (fingers crossed) I haven't replaced it since. Which is the longest I've gone on an ICM since about 2016.
Interesting. Do you have a pic of the heat sink installed ? Though I know it's not an easy spot to get a camera lol.
Which is the correct icm for a stock 1988 305 TPI?
I don't recall there being 2 different ac delco ones last time I ordered, maybe I've ordered incorrectly ?? Don't know if that would cause them to die quicker or not.
I think you want ICM: 10496048 which has been superseded to D1943A (w/o HEI). My notes on the subject are as follows:
ICM stamped '369' (AC Delco D1943A, GM 19179578): First used on the 1985-1993 Chevrolet Caprice with the 9C1 RPO Police option. This ICM does not retard timing starting at 3500 RPM, but provides 2 degrees additional advance from 4,000 to 5,000 RPM and a total of 6 degrees additional advance above 5000 RPM. GM replaced the "048" ICM with the "369" ICM. The replacement may not have "369" printed on it. The "048" was discontinued so GM felt like there was no need to differentiate between the two. If the AC Delco D1943A module does not have "369" printed on it, look for the GM part number 19179578 burned on the edge of the module. The 19179578 8-pin ICM was originally for the 9C1 Police Option in a Caprice. In 1989 GM made the AC Delco D1943A ICM (19179578) as the service replacement for all V6/V8 models through 1995.
ICM stamped '369' (AC Delco D1943A, GM 19179578): First used on the 1985-1993 Chevrolet Caprice with the 9C1 RPO Police option. This ICM does not retard timing starting at 3500 RPM, but provides 2 degrees additional advance from 4,000 to 5,000 RPM and a total of 6 degrees additional advance above 5000 RPM. GM replaced the "048" ICM with the "369" ICM. The replacement may not have "369" printed on it. The "048" was discontinued so GM felt like there was no need to differentiate between the two. If the AC Delco D1943A module does not have "369" printed on it, look for the GM part number 19179578 burned on the edge of the module. The 19179578 8-pin ICM was originally for the 9C1 Police Option in a Caprice. In 1989 GM made the AC Delco D1943A ICM (19179578) as the service replacement for all V6/V8 models through 1995.
Rockauto seems to make that part listing confusing with the notes. My replacement AC Delco distributor came with a 369 ICM and it has worked great, I kept the OE 048 as a back up.
Rockauto seems to make that part listing confusing with the notes. My replacement AC Delco distributor came with a 369 ICM and it has worked great, I kept the OE 048 as a back up.
It is super confusing. I have an 048 and it's one of the things I plan on correcting when my attention comes back around to the IROC-Z.
Thanks for all the info guys. I'm going to order the D1943A module and get the heatsink to add on with it, hopefully that takes care of it for a while.
I had to dig for it but I had one! You can see it’s just kind of there
RedLeader, so when installing, does the heatsink go on top of the plate on the distributor then the icm on top ? Using longer screws as you said. No issues getting the distributor cap back on ?
I had to dig for it but I had one! You can see it’s just kind of there
RedLeader, so when installing, does the heatsink go on top of the plate on the distributor then the icm on top ? Using longer screws as you said. No issues getting the distributor cap back on and plugging in the icm ?
RedLeader, so when installing, does the heatsink go on top of the plate on the distributor then the icm on top ? Using longer screws as you said. No issues getting the distributor cap back on and plugging in the icm ?
No you have to put it on the bottom side of the plate. The ICM will sit where it normally does. The longer screws will go through the icm, all the way through the baseplate, and then through the heat sink. You’ll have to put backing nuts on the screws to hold the sink in place and you will need to trim the sink a little bit to make it fit right.
If your gonna install a heatsink on the bottom of the distributor, I suggest that before you install it you clean the mounting surface well, and use a bit of the same thermal paste you'd use on the ICM itself on the heatsink where it mounts to the bottom of the distributor.
My thermal paste of choice is the brand called "Arctic Silver"
No you have to put it on the bottom side of the plate. The ICM will sit where it normally does. The longer screws will go through the icm, all the way through the baseplate, and then through the heat sink. You’ll have to put backing nuts on the screws to hold the sink in place and you will need to trim the sink a little bit to make it fit right.
Got it! Thanks for your help RedLeader! Hopefully this solves the problem.
Originally Posted by OrangeBird
Hi KR81,
If your gonna install a heatsink on the bottom of the distributor, I suggest that before you install it you clean the mounting surface well, and use a bit of the same thermal paste you'd use on the ICM itself on the heatsink where it mounts to the bottom of the distributor.
My thermal paste of choice is the brand called "Arctic Silver"
Thanks for the tip OrangeBird. I have this thermal paste I've used now, previously I've used what they send with the icm but this stuff I just purchased last week from our "geek" shop here in Australia, they deal in electronics and computer/ computer building related stuff, very cool shop.
Would anyone agree it may be a good idea to include in a 6 or 12 month service interval to clean off old thermal paste and replace with a new layer ?
I don’t think so as the paste isn’t what causes the failure, it’s really the part itself and its placement. Also if that did make a difference you’d need to have a much shorter service interval as typically they’ll fail before the 6 month mark if they’re going to.
Would anyone agree it may be a good idea to include in a 6 or 12 month service interval to clean off old thermal paste and replace with a new layer ?
Going on year 12 with Arctic Silver 5 between my cpu and heatsink on my computer, I think one good application should do you. The cheaper pastes dry out but the good stuff stays.
No you have to put it on the bottom side of the plate. The ICM will sit where it normally does. The longer screws will go through the icm, all the way through the baseplate, and then through the heat sink. You’ll have to put backing nuts on the screws to hold the sink in place and you will need to trim the sink a little bit to make it fit right.
RedLeader, I just got the heatsink in the mail,however the holes in it do not line up with the holes in the distributor plate and icm ? Did you have that issue with yours ?
RedLeader, I just got the heatsink in the mail,however the holes in it do not line up with the holes in the distributor plate and icm ? Did you have that issue with yours ?
I’m running a large cap HEI system, with the 4 pin ICM, so all I had to do was cut the portion of the heat sink off that I have circled in yellow here and the remaining holes lined up.
If yours isn’t like that then some additional fabrication will be needed.
RedLeader, I just got the heatsink in the mail,however the holes in it do not line up with the holes in the distributor plate and icm ? Did you have that issue with yours ?
Already in the garage pondering how to set it up, thanks again. 😁👍
I think I'll just have to forget about it tbh, trimmed it up to fit but I can't even get my hands in there to hold the heatsink in place let alone hold it and thread a nut on 😒😭
Well with a fair bit of rooting around I got it in, bending my hands and fingers ways I never thought I could 😆
Getting to the nuts underneath was the hardest part, had to cut down a spanner so I had room to turn it.
Hopefully this'll be the last icm I need in a while 🤞
Well with a fair bit of rooting around I got it in, bending my hands and fingers ways I never thought I could 😆
Getting to the nuts underneath was the hardest part, had to cut down a spanner so I had room to turn it.
Hopefully this'll be the last icm I need in a while 🤞
nice! Yeah the amount of times I dropped a nut trying to put mine on…infuriating. Hope it lasts a long time!
I had the same idea, but when I looked more closely at my D.U.I distributor, I found the billet aluminum ones are radiused on the bottom side, so I can't fit anything flat against it like with the flat plate on the factory distributor... Anyone have any ideas on how to make it work in my application. I had the idea to cut the two fins off the one side and sandwich it between the distributor and ICM, and have the heat sink fins stick out downwards, I know it would have to trim the distributor cap, but I'm not sure if there is room under the other components in there...
