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Thread: TBI ignition control module

  1. #1
    Electronic Ignition! typhoonss's Avatar
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    TBI ignition control module

    Have a question for all you TBI lovers out there. I have had this truck for just over 6 years. once a year the Ignition control module goes bad, this is the 2nd time it has completely gone out where the truck could not start but usually just kills the timing advance so I can at least limp home if needed. I have replaced all the power and ground cables in the truck with marine grade and marine heat shrink but this issue keeps happening. I have replaced the entire distributer with a GM delco one about 3 years ago. I have tried performance ones, gm replacements advanced auto ones, and have gone to the junkyard and got the one that came in the truck, no difference. Just trying to see if anyone has seen this issue as I have spoke to ultiple master techs and they have no idea.

    Thanks All

  2. #2
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    They don't like heat. In the past I thought the little grease packet that it came with it was dielectric grease but turns out it's a thermal paste. Some have gone to extreme measures and purchased the good stuff used with heatsinks on CPUs. I seem to recall someone on this site relocating icm away from the heat, too.

  3. #3
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    Bolt it on a 8mm thick piece of alloy on the firewall with some heat transfer paste to work as a nice sized heatsink I've had a few that start idling bad sitting in traffic heatsoaking normally sorts them out changing location

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    Have you replaced the coil,plug wires??

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    Super Moderator dave w's Avatar
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    The attached screen shots show a normal SA and very odd SA. I wonder if over time, your SA starts looking odd?

    dave w
    Attached Images Attached Images

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    Fuel Injected! dktool's Avatar
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    Quote Originally Posted by dave w View Post
    The attached screen shots show a normal SA and very odd SA. I wonder if over time, your SA starts looking odd?

    dave w
    That odd one looks like a limp mode, I thought the module only controls advance in limp mode, and under normal conditions it only signals cylinder static advance and the emc/pcm timing table does the rest. ??
    Dean

  7. #7
    Fuel Injected! tamperedchevy's Avatar
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    it seems most don't last long but every once in a while, one finds a good ICM that lasts a lifetime. dang even the acdelco ICM failed?
    are you running a modded computer?
    i just had one fail a few days ago(it was two weeks old) the one i replaced was fine. i shoulda left it alone. back to the point. i had just patched my 7747 with the spark advance hack and it failed that evening...coincidence?

  8. #8
    Electronic Ignition! typhoonss's Avatar
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    sorry been out all weekend. The ICM's have been in the stock computer when it was a 5.0 and failed, in a very light modded 350 with a new distributer and failed and now in my modded 357 and failed. The timing/SA does not look wierd. This time it died and the truck was not even warmed up, I was ideling for about 15 minutes but it was 50 degrees out, shut the truck off and 2 minutes later tried to start and no fuel as the ICM does control allowing fuel. I have had 3 different tbi trucks and this is the only one that has ever given me issues, all were modded and all had headers full exhaust, electric fans, ignition systems or msd coils and moroso 8.65 ultra 40 wires. The coil and wires are about 1yr old as I replaced them right after the ICM died a year ago, for some reason it is about every year which makes no sense. I am gonna try the Artic Silver 5 thermal paste I use on my overclocked gaming computers and see if that helps. I was just throwing this out there to see if anyone else has had this same issue where it dies once a year, I usually put about 10,000 a year on the truck. Anyway thanks for the responses.

  9. #9
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    Quote Originally Posted by delcowizzid View Post
    Bolt it on a 8mm thick piece of alloy on the firewall with some heat transfer paste to work as a nice sized heatsink I've had a few that start idling bad sitting in traffic heatsoaking normally sorts them out changing location
    Seem to recall if you do this, can't remember which wires but they need to be twisted...
    Last edited by stew86MCSS396; 03-26-2018 at 12:00 PM.

  10. #10
    Fuel Injected! tamperedchevy's Avatar
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    i had two icms go out in 3 weeks now. but my connectors where a little loose.(maybe they loose connection enough with engine vibrations to shorten the icm life?) maybe check your pigtails? also my GM icm never fails. but every aftermarket one failed so far. really leaning towards--maybe they are all junk? just some ideas..

  11. #11
    Electronic Ignition! typhoonss's Avatar
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    One thing I think I have noticed over all 6 of these icm's failing is that it dosen't crank as fast when I start the truck for about a month before it dies. I just think it is very weird it is every year, not a few months or at random times but almost exactly a year apart these things die and dosent matter if gm or aftermarket or performance ones they all fail same time about 1yr. So I am keeping a space in the truck, I have the tools to change it out quickly so if it happens I can change it. I will also see if next time it starts cranking slower when starting and see if that is a side effect before it dies. But we will have to wait for a year because that is the pattern so far.

  12. #12
    Electronic Ignition! typhoonss's Avatar
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    I have never seen a SA like that in any datalogs and I was datalogging the day before the icm went out. The only thing I notice is it gets harder for the motor to crank over or should say it's like the battery being low and cranking slowly but the battery is fine. Once I replaced the icm it cranked over normally. The icm is very weird piece, I have had it just take out the timing advance and the truck would still run 2x, I have also had it just die where there is no fuel or spark 3x and I have also had it take out the entire distributor.

  13. #13
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    Quote Originally Posted by dave w View Post
    The attached screen shots show a normal SA and very odd SA. I wonder if over time, your SA starts looking odd?

    dave w
    would you say my icm is bad Dave? when my engine gets up to operating temp, it acts like the timing is way advanced and is hard to start.

    attached is a screenshot of the wbo2 spreadsheet with the log pasted into it...

    sa 2021-03-12.JPG

    important to note, the battery voltage was around 13.5 most of the log, but at the end it was down to around 12.5v i originally suspected the erratic readings due to the voltage going south... the engine was also around 219 degrees at its peak....
    Last edited by grumbolt; 03-13-2021 at 10:33 AM. Reason: added voltage and temp data

  14. #14
    Super Moderator dave w's Avatar
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    I don't know if the ICM is faulty or not. Usually an engine won't start with a faulty ICM.

    The odd SA might be due to the data stream definition or .adx file.

    I would reprogram the chip with the Altitude Spark Bias set to ZERO degrees, leave the other parameters unchanged.

    dave w

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    Quote Originally Posted by dave w View Post
    I don't know if the ICM is faulty or not. Usually an engine won't start with a faulty ICM.

    The odd SA might be due to the data stream definition or .adx file.

    I would reprogram the chip with the Altitude Spark Bias set to ZERO degrees, leave the other parameters unchanged.

    dave w
    Leave the altitude bias alone. Not sure why people just program this out with no knowledge of what it is actually there for or what they are doing by removing it. The weird datalog SA is because the logging aoftware is not recognizing a negative number. Zero'ing the bias is adding that much timing to the whole timing map. If it was a bias of 9.81 and you set it to zero, you have added nearly 10° across the entire spark map.

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