Multiple Ignition Control Module Failures
 

Hello everyone. My 1995 Oldsmobile 88 Royale has me pulling my hair out! The car only has 74k original miles and is in like new condition from top to bottom. Recently the car started running really rough and was diagnosed by a competent mechanic as having a bad ignition control module. The module was replaced with a $325 unit from NAPA and the car drove great... for 1 week. Then it started running terrible again. He replaced the ignition control module again and the car ran great for 3 days before messing up again. These were boh Chinese modules. Then I found a USA made A/C Delco ICM on Rock Auto for $225. I was hoping this would solve the issue but after a few days of running great it started running terrible again. This car has OBD1 with the 16 pin OBD2 style diagnostic port so I haven't been able to pull codes. 2 of the 3 coils have also been replaced during the last month. Any idea why these modules are failing after only a few days? Thanks in advance.

It's 'possible' the swapping of the ignition control modules is really masking a poor connection on one of the ICM pins.
Perhaps try removing & reinstalling the connector (running the engine after each re-connection). If it does start running well, what I like to do is tug on each wire one-at-a-time in an effort to try to identify the specifical location of the bad connection.

https://cimg3.ibsrv.net/gimg/www.gmf...ecb514f5c5.jpg

Thank you for your response. I will give that a try.

Well, it certainly doesn't help that the first two modules were cheap chinese shit ones. Do. Not. Ever. Buy. Cheap. Chinese parts.

If the car runs great when its cold, then causes issues after it warms up, its ICM under the coil packs.

Did you by any chance scrape off any of the old thermal paste under the ICM and mounting bracket?

It was the repair shop that I went to that used the NAPA modules. I'm not sure how well the mating surfaces were cleaned in between module swaps but it's frigid here in northern Indiana right now so I don't know how probable 3 consecutive heat related failures would be... especially in just a few days. I forgot to mention that earlier today I tried a hard reset on the computer by disconnecting both battery cables and jumping them together for a couple hours. I also had the headlight switch on at the same time. The car ran the same after doing this but the check engine light never turned off. Shouldn't it have reset and turned off at least briefly? Maybe my computer is somehow involved in this? Thanks for your input.

The first 2 replacement modules were Echlin and the third was the A/C Delco module.
https://cimg3.ibsrv.net/gimg/www.gmf...6449bad461.jpg
https://cimg6.ibsrv.net/gimg/www.gmf...f8833dc093.jpg

I agree with the others, unplug/replug after the issue and see if it improves.

Also, check here:

https://cimg9.ibsrv.net/gimg/www.gmf...77915dbeb8.png

I've seen many cases where the insulation rubs through against the screw, which is grounded. That causes issues. Pulling the plug off then putting it back on makes it want to straighten the wires a little, but then vibration and heat and position make them want to flex back while driving.

Thank you for the information and suggestion. I will give it a try in a couple days when the outside temps get above freezing again. It's been in the single digits lately and I'm hesitant to mess with those connections when it's so cold. Any thoughts on why my check engine light won't reset when I disconnect the battery while also having the battery cables jumpered together and headlight switch turned on?

Your 95 system is not a true OBD 1 or OBD2 system. You are in the middle with a hybrid OBD 1.5 system. 1994-1995 was the testing years for the EPA phase to OBD 2.0(1996-newer)

Unfortunately for you, you need a diag scanner capable of OBD1 and OBD2 systems.

IMHO, Actron is your best bet. The CP9145 which is discontinued, you can probably find on ebay somewhere. If you do go looking for it, make sure it comes with all the needed cables.
If you have the big bucks, look for an old SnapOn scanner.

On another note, I remember from MANY years ago when the 3800 engine was the only engine discussed in here before corporate turned this forum into a shit show. There was many discussions that if you dismounted the ICM when cold, ran the engine and heated the bottom of the ICM with a hot air drier, it would cause issues. This was for testing purposes to determine if it was the ICM.

If your CEL is still on, I highly recommend getting the codes read, then post them here.