I have a 1985 740 GLE #1440 off the assembly line, with 294,000 miles, It has the Bosch ECU system and a NA 2.3L, It seems kill off ICM's (the one by the air box) in a short period of time, sometimes in minuets, or in a short drive a half mile away under hard acceleration.

Things I have tried to fix the issue .
Changed Distributor's (used), New caps and rotors brass only.
Changed Coils three different Bosch units (used) with good resistances I believe, and a crap no name Chinese one (new) with more resistance than the bosch ones, and a flame thrower II coil (new).
Tore apart the dash and cleaned every connection point on the wiring harness with deoxit and looked for any pins that were over sized and bet them back and used deoxit gold to get a better connection.
Cleaned ecu socket and pins same as the harness
Replaced the ECU
Cleaned all of the interior and exterior grounds in the engine bay and cabin
Cleaned all of the fuse connections same as the harness and the relays.
Replaced positive cable with a new brass gold plated heavy duty connector.
New plug wires
New NGK Iridium plugs
Refurbished Bosch starter
Refurbished Bosch alternator
It runs great when its running, I had a temporary fix work for the last 6 months or so I used the crappy coil with more resistance and it has been fine even under hard acceleration.
Until a week ago, the one used distributor had too much play in the rotor shaft and was grinding down the cap contacts on one side it broke the corner of the rotor and jammed up inside of the cap. I found it with one bolt in the distributor and it was cocked sideways and before I had found that I thought it was the module again so I got another one warrantied and replaced it and the starter because a friend said a old stater can cause a surge in the system and kill the module, and I have had a parasitic power draw issue and I had read that a starter can sometimes be the issue, it is 35+ years old and still works with no issue but what the heck give it a try.
Now the module is replaced and the starter changed and I changed out the coil to the old Bosch in hopes it was fixed with the starter and its still killing modules, car runs great and then it stalls then restart then it gets rougher running and it stalls again worse yet then dies and no starting anymore, pulse from the white and red wire from the dizzy but nothing out of the grey shielded wire from the module.
Any help would be wonderful it was my moms car and mine for close to 15 years and my first car to drive all of the time, we loved driving it and I still do sense she passed and now its mine that I daily drive.
I don't think it matters but it has been damaged in the rear of the car twice once from my mother and I replaced the hatch and fixed the drivers side rear corner, then again when I was towing it on a tow dolly to Washington from Oregon and was rear ended on the empty high way at 1:30 am with no one around stationary in one lane on the same corner I fixed I am still working on fixing that.

 

"UPDATE" I have replaced the distributor now and so far so good. Its a Autozone gold so potato quality for $270.
I talked to a European Master mechanic named Gary, I very nice man who was more than helpful he even tuned down cash for his time and info. What he told me is that when he worked for Saab and he repaired many a Volvo of that age is that the ignition systems are sensitive and DO NOT want too much resistance in the wires or the plugs Gary believed that it was not to exceed 8,000 ohms of resistance but it had been a while sense he had looked so not to quote him. He said that Volvo used their own Volvo plugs but that they were NGK's that were "modified" so the same cross numbered plug is not the same I have some old Volvo plugs so I will check the Ohms. Garry also said that he felt that he remembered the plug wires were solid core wires so I replaced my garbo resister wires and made some solid core wires from the leftover I had from my kit for my 51 GMC. It runs smoother now so it helps. The last thing's Gary said is that you need to stick to Bosch parts and that there is a capacitor on the coil that is in a square box If its bad it can help kill a module because it helps act as a surge buffer to soak up some of the spikes in the ignition system that can back feed from high resistance in the plugs and wires, it acts as a voltage spring.

I hope this helps anybody out there.

 

Check the ballast resistor in series with the high side of the coil. It is used to limit the current through the coil and ignition module. The voltage at the coil positive terminal should be less than 12V when the engine is running.

 

OK I will thank you for the info.

 

Sense i have changed the spark plug wires the ICM has not died in all this time. I checked the ballast resistor and it was fine.

 

The ballast resistor is by passed by the starter solenoid when the engine is cranking to give full battery voltage to the coil. Once the engine starts the resistor is back in the coil circuit and drops the voltage at the coil positive to about 6 volts. If the ballast resistor is bypassed all the time it can burn out the ignition module.

 

That is correct like a gm vehicle with points.