1990 Olds 88 - Bad ECM suspected
 

Good evening all. I am fairly confident I am on the hunt for a new ECM, but I just wanted to review the symptoms to make sure I am on the right track.

Plain and simple, the car is possessed.

As mentioned in my "Your ride" thread, I have been battling an intermittent stalling issue with this car.

I swapped the problematic Magnavox ICM with the newer Delco style system, and it seems to have improved drive-ability. It also was previously acting like it was intermittently down a coil, which is a symptom that has not returned since. The battery was disconnected when the ICM was replaced, so all codes were cleared at this point, on Friday.

Since then, I have been primarily driving this car, as it has been behaving well enough to not be an extreme hazard, and it needs to have its legs stretched out finally.

But, it intermittantly bucks, misses, and stalls.

Soon out of the gate, SES light comes back on intermittently as well. First scan after a drive of a few miles reveal codes 14, 27, and 44. Soon after, 13, 14, and 42 joined the party.

Then, on the way to work, it drove great, up until the last mile or so, when the SES light came back on, and the car started running just a little off, as if it was not quite running perfectly. After parking, I tried scanning, only to find the scanner wasn't able to connect to the computer (it would just hang, or would give a communication error). Once it finally did connect, it indicated there was 40+ error codes. The only code I could verify the car WAS NOT throwing was code 64 (EGR Solenoid 2), only because I could see 63 and 65 codes listed (EGR Solenoid 1 and 3). Out of disbelief, I scanned it again, only to find 12 codes set this time (I didn't make note of the list at this point), but it spans multiple systems, with even some codes directly conflicting with one another (such as too high and too low).

My current plan is to check/reseat the firewall connector, check for major wiring flaws, and possibly reseat the connector on the ECM, in the event setting for 5 years has played an impact, but I am suspecting the ECM is cooked.

It would also make sense because the previous owner was an old mechanic, who kept it on the most archaic of battery chargers, so it is entirely possible modules may have been over-volted or suffered reverse polarity.

I welcome any thoughts, questions, or feedback at this point.

Are the battery and alternator operating up to spec? Nothing gives you electrical gremlins more than a battery that is about to fail or an alternator that isn't doing its job.

*Update*

At your suggestion, I stopped by Autozone for a charging system test.

The battery failed. Replaced battery under warranty. Alternator passed, however I am not sure if the full gambit of tests was thrown at it.

I scanned it again once I got home as the SES light had come on again. Only code 44 (System lean) has appeared so far.

Guess I'll keep rolling a bit to see how this develops.

At best, you may have found your problem. At worst, making sure the charging system is operating up to specifications is a good basic start when diagnosing electrical problems.

If the charging system is now fixed, and the only code you have is 44, you obviously have a lean condition/exhaust leak....

If multiple codes return, those early 90's ECM's were bad, even the rebuilts.....

Try a tap test on the top of the ECM, with vehicle at normal operating temp, the vehicle in gear, and brake applied....if the engine stumbles, or the CE light comes on while tapping, you found your problem.....however, the est is not foolproof...nothing may happen, but the ECM may still be bad.....

however, the test is not foolproof...

I have a 1990 Olds 88 as well and it does all kinds of funny things like this too.

Possessed is the perfect word to describe these 90 88s.

I had a problem with mine once with a stalling issue. After months of trying to narrow down the problem it ended up being a plug right next to your fuel rail and it connects the ignition module, Crank, and Camshaft to your computer. On my car the pins inside of that plug would get hot after 30 mins or so and it would lose contact and the car would die. Give that plug a good shake and see if your car spits and stalls like mine was doing. Can't hurt to check.

Good Luck,

Matt