Ignition Control Module

[scitzz]

I had one go out on me recently. I had another 93 here at the time that was running to test it out, and was able to isolate that it was the problem. I ALSO have a 93 here that isn't running, that I grabbed an ICM off of to get my car going. Cleaned the mounting surface really well, used thermal paste of the type that you use for mounting CPU's, and installed it. Ran fine.

All night I have been doing a bunch of work on my car. New intake gaskets, and conduit for all the wiring. Tightened the sometimes squealing alternator belt. Odds and ends, trying to polish off this B6 swap in time for Madness. Start her right up, and letting her run and warm up. Start putting things away, and just like a few weeks ago, she cuts off in an instant, Deja Vu, right?

Pull a plug, check for spark, nada. Swap in a known good coil. Nada. I am thinking ICM again, and Oreilly has one in stock.

What I am trying to figure out, tired as heck, and ready for bed, is two things. One, is there another test to be SURE it is the ICM, and is there something that could be causing them to go, or was it bad luck, both 20 year old parts just went? The first one to go had NO paste left on it, and when I pulled the other, it didn't appear to have any either. I have no idea the history of that car, or how long it has been since it ran....

[htchbck]

They sometimes just like to go randomly, but having two in a row bite it makes me wonder if there might be something causing it. FWIW all the late 80s/early 90s mazdas I've ever looked at have the same ICM. protege, 323, mx3/5/6, 626, mpv, and of course EGTs. I always get a couple when I'm at the yard, I have probably over a dozen, they usually charge less than 2 bucks a piece for them. Cheap insurance to throw a couple in the glovebox just in case. Though I've only ever had one go out on me, I've heard plenty of stories of them going bad.

[bravekozak]

I burned one out when I put in a Accel super coil without the inline fuse to protect it. Now I always use a fuse.

[DON SVO]

I had one go out on me recently. I had another 93 here at the time that was running to test it out, and was able to isolate that it was the problem. I ALSO have a 93 here that isn't running, that I grabbed an ICM off of to get my car going. Cleaned the mounting surface really well, used thermal paste of the type that you use for mounting CPU's, and installed it. Ran fine.

All night I have been doing a bunch of work on my car. New intake gaskets, and conduit for all the wiring. Tightened the sometimes squealing alternator belt. Odds and ends, trying to polish off this B6 swap in time for Madness. Start her right up, and letting her run and warm up. Start putting things away, and just like a few weeks ago, she cuts off in an instant, Deja Vu, right?

Pull a plug, check for spark, nada. Swap in a known good coil. Nada. I am thinking ICM again, and Oreilly has one in stock.

What I am trying to figure out, tired as heck, and ready for bed, is two things. One, is there another test to be SURE it is the ICM, and is there something that could be causing them to go, or was it bad luck, both 20 year old parts just went? The first one to go had NO paste left on it, and when I pulled the other, it didn't appear to have any either. I have no idea the history of that car, or how long it has been since it ran....

Did you use thermal grease on the mounting plate for the ICM when you swapped it?

[WmWatt]

You can take it to some auto parts stores for a free test, usually the stores who advertise free battery and alternator tests. There's only the one manufactuer in Japan and one importer as far as I know (Standard?) but retail prices vary widely. Copy down the number and take that to the junk yard if you want to look at other Mazdas. Or better yet take the buned out one.

[scitzz]

When I was at the JY last week, I even found an old Mazda to pull the IAC, and distributor connectors from, and meant to get the ICM, but forgot, what with being rushed out

I am going to have to hunt them down.

Did you use thermal grease on the mounting plate for the ICM when you swapped it?

Please see the second to last sentence of the first paragraph I am thinking that should be the same stuff.

[scitzz]

WulgartheGreat is on his way over with his 93. I will plug mine into his to see if his won't start, and if not, run to get a brand new one.

Anyone else know if there is something that might be frying them out?

[DON SVO]

When I was at the JY last week, I even found an old Mazda to pull the IAC, and distributor connectors from, and meant to get the ICM, but forgot, what with being rushed out

I am going to have to hunt them down.



Please see the second to last sentence of the first paragraph I am thinking that should be the same stuff.

Some people will use dielectric grease and not the white stuff from Radio Shack. Seen many a burnt up TFI/ICM because "dielectric grease, yo!"

[scitzz]

AH. No, I used thermal paste, the white stuff, like you could buy at the Shack.

[DON SVO]

WulgartheGreat is on his way over with his 93. I will plug mine into his to see if his won't start, and if not, run to get a brand new one.

Anyone else know if there is something that might be frying them out?

you mentioned redoing some wire loom, is there anything on the power side that could be shorting to ground?

[scitzz]

Don, maybe. My friend just showed up with his 93, swapped my ICM in, worked fine.

I am ruinning on only a couple hours asleep, and am only half awake. Bolted my ICM back up, started checking wires, found a little break in one running to the dizzy. Wrapped it up, still no spark. Swapped in a dizzy. No spark. Start looking things over. NEVER PLUGGED IN THE ICM!

Blech. Yawn. Plug it in. Fires right up.

Now I don't know if it was the dizzy, or the crack in the wire, but I will find out later. I am going back to bed!

[DON SVO]

Don, maybe. My friend just showed up with his 93, swapped my ICM in, worked fine.

I am ruinning on only a couple hours asleep, and am only half awake. Bolted my ICM back up, started checking wires, found a little break in one running to the dizzy. Wrapped it up, still no spark. Swapped in a dizzy. No spark. Start looking things over. NEVER PLUGGED IN THE ICM!

Blech. Yawn. Plug it in. Fires right up.

Now I don't know if it was the dizzy, or the crack in the wire, but I will find out later. I am going back to bed!

They tend to die from overheating and shorting. They act as a buffer to the ignition system and are designed to die before the ECM does in the event of an electrical issue. If there's a crack in the wire and it grounded out, the ICM will cook. You might have just gotten a bad luck draw on the 2nd one, or there could be an underlying issue causing it.

[scitzz]

Sorry, I wasn't perfectly clear, lack of sleep and coffee!

My ICM was fine. I have a feeling it was the wire with the crack grounding out, it was, IIRC, the middle of the three that go to the dizzy, which is a "powered" wire. I have had issues with that wire once before. All of mine are getting old, and are susceptible to cracking. I even had a thread on here asking about ways to bring back the "suppleness" of the wires.

So, I have wrapped most in new tape, and am working on covering all the wires in the engine bay with plastic conduit cover. A little bulky, to say the least, but I am hoping to extend their lives, and stop problems like this again!

I hadn't made it to this section of wiring yet So of COURSE it tricks me!

[gauge_half_inch]

I've have those wires at the dizzy plug crack and just randomly loose connection, car dies. You could push the wire into the connector and have someone crank it, it would fire every time, let go, it dies.

[DON SVO]

If y'all want a website to buy the EEC pins and late model OEM wiring from I have some.