TBI ignition control module

**typhoonss** · 03-23-2018

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

**stew86MCSS396** · 03-23-2018

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.

**delcowizzid** · 03-23-2018

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

**C2500** · 03-23-2018

Have you replaced the coil,plug wires??

**dave w** · 03-23-2018

The attached screen shots show a normal SA and very odd SA. I wonder if over time, your SA starts looking odd?

dave w

**dktool** · 03-23-2018

Originally Posted by dave w

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. ??

**tamperedchevy** · 03-25-2018

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?

**typhoonss** · 04-11-2018

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.

**grumbolt** · 03-13-2021

Originally Posted by dave w

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....

**dave w** · 03-13-2021

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

**stew86MCSS396** · 03-26-2018

Originally Posted by delcowizzid

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...