I have had two different GT's stall out unexpectedly in the last couple of weeks. Both occurred on very hot days
The first in my stock 87 GT occurred after about 15 minutes at freeway speeds. It simply quit and I was forced to coast over 3 lanes through busy traffic to get to the shoulder. I immediately tried to restart without success so I called AAA for a tow. I suspected the ICM. Normally I carry a spare ICM, thermal paste and tools but I was close to home and they were all in another Fiero that day as luck would have it. Besides which, I had no wish to attempt the repair on the shoulder of the freeway a couple of feet from roaring traffic.
While I was waiting for the tow I tried to start it a couple of times. After about 20 minutes I was able to get it started. I was only a few miles from home so I decided to try it. I got to the next overpass and another mile back the way I came and it stalled out again. Literally across the freeway from the original stall. After redirecting AAA to my new location they got me home safely.
The next occurrence came soon after as Jenny was driving her 86 GT (5 speed 3.4L) to work when it stalled out at a traffic light shortly after a 20 minute run up the freeway. She was unable to restart immediately and AAA got her home as well. Since then I have twice been able to start the car and run it in the driveway for about 20 minutes before it just quits. Again, high valley temps here but not an overheat issue.
I've only ever had one other ICM failure some years back (88 GT auto 3.4L) and that was also on the freeway on a hot summer day. It also restarted after a period of time and I was able to limp home.
I swapped the new ICM spare into the 87 and it seems to be OK now. I do have some spare junkyard ICM's but I don't want to risk an old part in her car with her commute.
I tried ordering the ICM from Amazon since it was GM, the price was right, free shipping and I could get it next day. Unfortunately, I was unable to complete the purchase. Amazon stated that the item could not be shipped to my address and stated several reasons why that might happen, but without being specific as to which reason it was. None of them seemed applicable in this case (ie: oversized package, etc.) I tried two different addresses (different cities and zip codes) in California but no go. I'm guessing it has something to do with the California Prop 65 warning about cancer causing products, which is completely ridiculous in this case. I think these sellers just put it on anything just to avoid the necessity of actually researching it. Really ticks me off.
Anyway, I have a new GM ICM coming from the Fiero Store now. Higher price, slower delivery.
So, since all three cars were able to restart after a cool down and run for a period of time after the initial failure I'm wondering if the ICM's are really failing, or if they just need to have the thermal paste refreshed. In all 3 cases the old paste had dried up and flaked away leaving just a slight dirty residue. I'm tempted to try this on her 86 GT before the new ICM arrives just to test the theory (if I can find the time).
I usually transfer all my trunk necessities, including ICM supplies, to whichever car we are driving when taking a trip out of town (we have 4 daily drivers) but I am wondering if a couple of hand tools and a tube of thermal paste might be a useful thing to have in each glovebox for when a new replacement ICM is not handy.
If the module is already fried, replacing the thermal paste will not bring it back to life. However, if you can restart it after it cools down, the module is not completely dead. In that case, I would think replacing the thermal paste may extend the lifespan but it is already on the brink of failure anyway and you should replace it before it dies permanently leaving you on the side of the highway again
Yes, your ICMs (or their wiring) are really failing. When they get hot the circuit boards expand and eventually a trace breaks. When they cool off, the trace re-connects and it seems like all is well, but it will happen again. If you can find no problems with the wires and connectors, the ICM is not trustworthy. I don't have any idea about the delivery problems.
Very likely Repeater ICM Failures are Symptoms of other problems... like iffy wiring, mounting screws, main I-coil and more. Highlights See my Cave, HE Ignition
Thermal "paste" going "Dry" has little to No effect on parts using it. Stop believing BS pushed thru-out the PC building world and everything since. I use Permatex Brake Grease instead because is plastic safe, allows more metal to metal contact and seals out water and other crap. Beside use for brake jobs and can get easier at most part places...
------------------ 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)
I had this happen to me on Redwood road.....coasted to a stop, let it cool off, and then swapped the ICM and it started right up- make sure you buy the higher grade ("Professional grade")ACDelco unit- I did hear a good review of the Davis Unified Ignition unit.....Not sure I would name my company "DUI" but maybe I am square.....
I have a spare unit in my car with a tube of the conductive paste- and, of course, the tools to change it out.
I would suggest the D.U.I. DynaMod ICM. This one was taken from my '95 Silverado after I wrecked it. It has lasted quite a while as it was in the truck for around 4yrs and now in the formula for about 5yrs. Just now put the heat sink on the bottom of the distributor.
I have the D.U.I. coil as well.
Brian
[This message has been edited by BHall71 (edited 07-05-2022).]
I have had ICM failures and later put them back in and run for long periods. Early in my Fiero history, I would keep a failed ICM and keep swapping until it met its final death. Some feel that the circuit traces separate under heat loads and reconnect at cooler temps. Of course this practice will one day leave you stranded. The one GM module I have ever bought only lasted less than a month. Echlin or Standard have been my choice and I've not had a failure in probably 10 years or more.
Just my 2 cents here, but when I was designing PCB's for computers, we ran into similar problems when the PCB's where tested under various thermal loading conditions. When the boards began to fail, and it wasn't due to a bad component or IC, they would almost always fail where there was metal to metal connections that were soldered together, or in other words, where the components touched the copper traces. The thermal stresses on certain joints would cause them to fail after some time, but what we would find as the cause, was a bad solder joint. During the design phase, this happened a lot, mainly due to the cheaper materials used, and the wave soldering machines used in the 80's and 90's. When the wave solder machines were not set up properly, you could get a LOT of bad solder joints. When most boards went with SMD components, most manufacturers switched to reflow soldering, which fixed most, but not all, of the soldering issues of the past.
A trace separation would most likely be caused by mechanical stress, and not heat...generally. Heating a trace with a crack in it, would not cause it to fail. More likely it would be the other way around. Cooling it would shrink the trace, separating the ends where it was cracked, and heating it would rejoin them and make it work again. However, when you are talking about heating soldered joints on IC's or other components, a failure developing from a rise in temperature would be what I would expect, and also explains why, when cooled, it works again. This was referred to as "mechanical creep" due to thermal stress. This was particularly bad on some designs using BGA (Ball Grid Arrays) IC's, and would cause the same failure scenario due to heat. Fixing this in most PCB designs required mechanically attaching the IC to the PCB, usually with epoxy glue.
Of course, a passive component that is far enough out of spec, could also explain what is happening. When its cool, it is just far enough in spec to operate correctly. When heated, it falls out of spec, causing the circuit malfunction.
Apologies for the long winded response...
[This message has been edited by computer_engineer (edited 07-07-2022).]
Wave soldering likely was used for ECM, Chime box, and a lot more in 80's vehicles. BIG Problem is big vs small parts and clearance etc of holes. Example: See my Cave, Chime Box Defect & Connection notes
Worse, Many GM OBD1 ECM had known Defect as Conformal Coating used would swell over time and lift parts off the board.
ICM and a few other parts are Made to take a lot more heat vs just about everything else that have problems if used when Ambient Air > ~ 100 to 120°F because can't dump heat generated by them and junction temps pushes 160 to 180°F. Example: If I leave a Dash Cam mounted behind RV Mirror on while parked, soon the unit will crash when cabin air temp gets high often way before reach max temps in https://www.fiero.nl/forum/Forum2/HTML/141784.html
But Repeated ICM Fails will happen when other parts are iffy to outright "dead" making the ICM to heat up way more then spec. On top many are missing Heat Shields blocking IR from exhaust heating the thing too.
Originally posted by theogre: Wave soldering likely was used for ECM, Chime box, and a lot more in 80's vehicles. BIG Problem is big vs small parts and clearance etc of holes. Example: See my Cave, Chime Box Defect & Connection notes
Yeah, those wave soldering machines took hours to set up correctly. On one of my first modem designs, when I visited the facility where they were being made, they spent the majority of the first day getting the machine set up. It was interesting to me how long they were used, even when reflow started being used. I am sure it had everything to do with money, as the reflow setups actually added a few steps in the process, and therefore, added cost...at least at first. But they were much easier to setup and control, so quality went up.
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Worse, Many GM OBD1 ECM had known Defect as Conformal Coating used would swell over time and lift parts off the board.
I think I have seen a few boards like that. That issue can be caused by poor temperature/humidity control during the curing process. I never designed any PCB's that needed a conformal coating, but all of them used solder masks, which, although they used different materials, suffered from the same issues, if they were not applied correctly or cured properly. Polymers were generally used for the mask, and I believe urethane compounds were used for the conformal coatings. I am not sure what was used on the ECM's for the Fiero.
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ICM and a few other parts are Made to take a lot more heat vs just about everything else that have problems if used when Ambient Air > ~ 100 to 120°F because can't dump heat generated by them and junction temps pushes 160 to 180°F. Example: If I leave a Dash Cam mounted behind RV Mirror on while parked, soon the unit will crash when cabin air temp gets high often way before reach max temps in https://www.fiero.nl/forum/Forum2/HTML/141784.html
I really enjoyed reading your posts when you used the Arduino and the thermocouples to collect temperature data in the engine bay. Makes me want to go dust off my Raspberry Pi's and try a few projects myself.
Hey buddy, I have had an ICM go out on me before so I too keep a spare one in my trunk. I would also suggest keeping a spare ignition coil in your car too. I had one go out on me before and leave me on the side of the road. It is even easier to switch coils by taking the connections off the one you have on the car and connecting up the spare one without even taking the old one out. Just let it float in the air and try starting the car. If it starts and you aren't too far from home, you can drive home and replace it properly when you get home. Just a suggestion.
Hey buddy, I have had an ICM go out on me before so I too keep a spare one in my trunk. I would also suggest keeping a spare ignition coil in your car too. I had one go out on me before and leave me on the side of the road. It is even easier to switch coils by taking the connections off the one you have on the car and connecting up the spare one without even taking the old one out. Just let it float in the air and try starting the car. If it starts and you aren't too far from home, you can drive home and replace it properly when you get home. Just a suggestion.
Or just keep a piece of twine with it to tie it up against the old one until you get home.
