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Yellow-88
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JUL 23, 02:55 PM
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Hi
It's always been my experience that an ignition control module will just plain fail. Sudden no spark, no fuel. But ... it looks like they can just "act up".
Because the tachometer sees ONLY primary ignition, an unsteady tach is the first symptom of a primary ignition issue. As it gets worse, hesitation, sag and stumble along with bouncy tach needle sets in. If letting it cool off temporarily fixes the problem, it's a half cooked ICM.
The ICM cools it self by heat sinking into the distributer base that lives in a hot environment. Not a great design.
Any ideas on how to help keep it cool? I'm considering better heat shielding design for one.
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Patrick
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JUL 23, 03:38 PM
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| quote | Originally posted by Yellow-88:
Any ideas on how to help keep it cool?
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Installed heatsink on distributor under ignition module
| quote | Originally posted by Yellow-88:
I'm considering better heat shielding design for one.
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In addition to the heat sink I installed 16 years ago (and that ACDelco ICM is still working just fine), I also installed a much larger heat shield extension protecting the distributor from the heat of the EGR valve and tube. The white arrows indicate the two ends of the shield. It extends right down to the intake manifold. This required that the coolant tubes to the TB also be removed, but the side benefit of this is that there's now less heat in the immediate area around the distributor, as the coolant tubes themselves get plenty hot.
 [This message has been edited by Patrick (edited 07-23-2024).]
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theogre
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JUL 23, 06:33 PM
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When you have "Bad ICM" often isn't just "Bad ICM" but other things killing it.
Heat Sink can help or not depending what else is killing it.
Pull tach filter because that can cause ignition problems then kill the ICM.
See https://web.archive.org/web...t/~fierocave/hei.htm------------------
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
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cartercarbaficionado
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JUL 23, 07:21 PM
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| quote | Originally posted by Yellow-88:
Hi
It's always been my experience that an ignition control module will just plain fail. Sudden no spark, no fuel. But ... it looks like they can just "act up".
Because the tachometer sees ONLY primary ignition, an unsteady tach is the first symptom of a primary ignition issue. As it gets worse, hesitation, sag and stumble along with bouncy tach needle sets in. If letting it cool off temporarily fixes the problem, it's a half cooked ICM.
The ICM cools it self by heat sinking into the distributer base that lives in a hot environment. Not a great design.
Any ideas on how to help keep it cool? I'm considering better heat shielding design for one. |
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oh yeah dealt with killing 14 of them a year ago since the only one that worked had a wandering idle. long story short a dying or out of whack pickup will kill these very fast
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Yellow-88
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JUL 23, 07:25 PM
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Hi
I said that the tack sees only the primary ignition ... ( and I'll add) ... and that includes the tack filter. Anything happening in the primary ignition with affect the tack. It's just that the tack is very sensitive and will show tiny PI issues before you feel them.
I like the fined heat sink addition. They are readily available sized to fit our distributor. Like the module, they need thermal paste.
But they're still in a nasty hot place. So a better heat shield is a logical addition. Heat shields keep the JWT from frying so it makes sense to me.
I think I found a better ICM. Is anyone familiar with this one?
https://www.summitracing.com/parts/acc-35370
https://www.summitracing.co...Y-Pp9vxoCr3gQAvD_BwE
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cartercarbaficionado
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JUL 23, 07:33 PM
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| quote | Originally posted by Yellow-88:
Hi
I said that the tack sees only the primary ignition ... ( and I'll add) ... and that includes the tack filter. Anything happening in the primary ignition with affect the tack. It's just that the tack is very sensitive and will show tiny PI issues before you feel them.
I like the fined heat sink addition. They are readily available sized to fit our distributor. Like the module, they need thermal paste.
But they're still in a nasty hot place. So a better heat shield is a logical addition. Heat shields keep the JWT from frying so it makes sense to me.
I think I found a better ICM. Is anyone familiar with this one?
https://www.summitracing.com/parts/acc-35370
https://www.summitracing.co...Y-Pp9vxoCr3gQAvD_BwE |
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yeah a fiero owner a few towns over is running one. he says like the rest it's a hit or miss on how it runs between modules. sometimes you get a bat out of hell and other times it's just slow. he does have a killer custom intake and performance mods so I'm inclined to believe him
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Yellow-88
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JUL 23, 07:36 PM
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| quote | Originally posted by cartercarbaficionado:
oh yeah dealt with killing 14 of them a year ago since the only one that worked had a wandering idle. long story short a dying or out of whack pickup will kill these very fast |
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Hey Carter
That's 14 hundred dollars in ICMs. Yicks ..... or where they the "economy" ones?
Is that true? Can a pick up coil issue kill an ICM? What else can?
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cartercarbaficionado
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JUL 23, 07:39 PM
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| quote | Originally posted by Yellow-88:
Hey Carter
That's 14 hundred dollars in ICMs. Yicks ..... or where they the "economy" ones?
Is that true? Can a pick up coil issue kill an ICM? What else can? |
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I tried a mixture of economy and oem ones and a performance one and believe it or not the best one was the cheapest one autozone had. had the most power and best fuel economy and screamed to 6k quite fast but didn't last long.
for longevity apparently the best ones are Delphi but that was the one that ran like crap. but it did run the longest out of any so there's that.
yeah the modules are pretty fragile and a whacky pickup like mine which was pretty much always telling it to fire slightly (not fully just enough to make it try over and over) will kill it in short order
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Patrick
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JUL 23, 07:46 PM
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| quote | Originally posted by Yellow-88:
I think I found a better ICM. Is anyone familiar with this one?
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Better than what? Better than a genuine ACDelco unit?
It's rather small. The finned area is very limited.
In regards to the pickup coils... they're inexpensive, and it should be standard practice to replace them when the ICM is replaced.[This message has been edited by Patrick (edited 07-23-2024).]
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Yellow-88
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JUL 23, 08:15 PM
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| quote | Originally posted by Patrick:
It's rather small. The finned area is very limited.
In regards to the pickup coils... they're inexpensive, and it should be standard practice to replace them when the ICM is replaced.
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Better meaning that it "may" be built to a higher standard than OEM because it's intended for competition use. Accel offers one for OEM replacement also at the same price as ACDelco. There are also ICMs listed for marine use by suppliers who sell to that industry. Are there different standards?
Yes I know about pickup coils. Green patina means the copper is exposed, because the insulation coating has fried. It's a good chance to clean the distributor body also.
Yes the store bought heat sink is small but bigger than the bottom of the distributer alone.
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