Wha? Why are you "all over the map".. different models and years had real differences. And I think that you are trying to solve repair issues with software versions. Why would 3 EPROMS fail? They rarely do.
1: April 2015: Engine quit while driving just like the key was turned off. No warning or unusual behaviour or noises. Spark tested ok, fuel was spraying into TB, valve train was moving. Had a spare ECM from the 2.5L 5 speed I'd taken out of my '86, so I tried it and the engine started right up and ran normally. The shift light wanted an up-shift to the 5th gear that's not there. I swapped the '84 PROM into the '86 ECM to see if the shift light would work properly, but the idle wouldn't drop below 2500 RPM, so I put the '86 PROM back in.
2: Car ran fine until July 2017, when the engine quit just like in April 2015.
3: I obtained an '84 ECM from a local source, installed it and the engine started right up and ran normally. The shift light wanted an up-shift to the 5th gear that's not there. Didn't care. Erratic idle variations developed, so I got another ECM from the same local friend.
4: The hesitation issue developed. Went back to previous ECM; tried the original '84 prom again and normal operation returned. Shift light works.
So, I'm wondering if the occasionally erratic alternator voltage output damaged the ECMs. And was wondering about all the different numbers on the ECMs and PROMs. Then I saw the chart Raydar supplied. Why are there 17 PROMs for '87 & '88 2.5L engines?
[This message has been edited by David Hambleton (edited 12-08-2017).]
1987 & 1988 used a different ECM, DIS instead of a distributor and the PROM is in no way swappable with an 84 ECM.
Your 84 just dying at times would tend to be an electrical issue. One area of problems with the 84 is that GM used the positive solenoid bold on the starter as a power distribution post. Start the car and wiggle with wires and see if it dies. A second place to worry about is the two power wires in your C500 that feed power from the engine to the fuse box. Again start the car and wiggle those connectors and see if the engine dies.
Originally posted by David Hambleton: ...Why are there 17 PROMs for '87 & '88 2.5L engines?
Different codes were released to address drivability issues that were encountered. One, in particular, was a "spark rattle" at part throttle. I'm not sure about the others.
1987 & 1988 used a different ECM, DIS instead of a distributor and the PROM is in no way swappable with an 84 ECM.
Your 84 just dying at times would tend to be an electrical issue. One area of problems with the 84 is that GM used the positive solenoid bold on the starter as a power distribution post. Start the car and wiggle with wires and see if it dies. A second place to worry about is the two power wires in your C500 that feed power from the engine to the fuse box. Again start the car and wiggle those connectors and see if the engine dies.
Yep; I'm aware of the changes in '87. I put an '87 engine in my '86 - changed the '87 water pump to the '86 and made a custom fuel line. Other than that it was fasten it up & plug in the '87 ECM. No issues since Oct 2013.
I agree the '84 dying would be electrical. No faltering, just off like turning off the switch. Had spark, fuel and valve train action. Put the spare '86 ECM in and started right up. Tried the '84 ECM again to no avail. I don't understand how the ECM could prevent it from starting with spark, fuel and valves working. The next time it quit I did nothing but change the ECM and it started right up.
I've since changed the alternator (to change the voltage regulator really) since the voltmeter was occasionally reading high. Maybe the fluctuating voltage affected the ECMs somewhat somehow...
Different codes were released to address drivability issues that were encountered. One, in particular, was a "spark rattle" at part throttle. I'm not sure about the others.
Originally posted by Raydar: Different codes were released to address drivability issues that were encountered. One, in particular, was a "spark rattle" at part throttle. I'm not sure about the others.
Also some #'s are likely "California chips" while others are "Federal chips" used by all other states.
------------------ 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 don't see any matching numbers anywhere between the chart Raydar supplied and the PROM TSB list. There are matching numbers on the 87-88 DIS Duke ECM list. I don't know what PROM is in my '87 ECM, but it works fine.
[This message has been edited by David Hambleton (edited 12-09-2017).]
Originally posted by David Hambleton: I don't see any matching numbers anywhere between the chart Raydar supplied and the PROM TSB list. There are matching numbers on the 87-88 DIS Duke ECM list. I don't know what PROM is in my '87 ECM, but it works fine.
Read the cave pages and TSB text. Chart # above are ON the PROM and often On the OE ECM too if label is still there. TSB # are reported to ECM Scan Tools. Two lists will NEVER match w/o a crossref list.
TSB is to fix specific problems. If you don't have the problem(s) then no need updated one. Some have knock or other issues in TSB table 2, checked for vac leaks etc w/ 0 results then got update PROM and then run w/o problems. My case: Before the update, going uphill and low speeds often cause knocking. After update the problem is gone.
Here's the original '84 ECM with the factory labels:
Here's the original '84 PROM: (The obscured PROM number is 0203)
So, I'm a little confused: Ogre's info is the 860122 on the ECM lable indicates there's an '86 PROM; internal #0122. The PROM pic shows DDB0203, which is an '84 PROM number. The engine was replaced under warranty in March 1988 under campaign 8A05 for a cracked block. There's no mention of the ECM or PROM in the 8A05 documentation that details all the parts to be replaced/re-installed and the labour for each item.
Anyway, it seems to me that it would be convenient to have the internal and external numbers match on the PROMs.
Alternatively, a cross reference chart would help, particularly if it identified the issue addressed by the PROM change. There must be a document somewhere... Maybe Mary Barra knows. Wasn't she involved in the Fiero electrical group?
So, I'm a little confused: Ogre's info is the 860122 on the ECM lable indicates there's an '86 PROM; internal #0122. The PROM pic shows DDB0203, which is an '84 PROM number. The engine was replaced under warranty in March 1988 under campaign 8A05 for a cracked block. There's no mention of the ECM or PROM in the 8A05 documentation that details all the parts to be replaced/re-installed and the labour for each item.
Anyway, it seems to me that it would be convenient to have the internal and external numbers match on the PROMs.
Alternatively, a cross reference chart would help, particularly if it identified the issue addressed by the PROM change. There must be a document somewhere... Maybe Mary Barra knows. Wasn't she involved in the Fiero electrical group?
I must have missed that "860122" comment. I looked at both of the links he posted and didn't see it.
The label on your ECM clearly shows the DDB broadcast code. This is the same code that's stamped on your PROM. The 3 or (usually) 4 character alpha code is all I ever use when I'm describing Fiero PROMs. If your car was in for service in 88, it's possible that a new ECM and PROM with the "860122" date code was installed, as part of the repair. It still would have been for an 84, since that's what yours is. Just because that DDB code is designated for an 84, doesn't mean that it couldn't have been produced way after the fact - like 1986.
Also... You mentioned that you swapped in an 86 ECM in place of your 84's. I didn't think that was possible. I thought the 84 ECM was "year specific". Although I suppose that even though they were different, the pinouts on the connectors could have been the same. What also surprised me is that you were able to swap PROMs back and forth between the two different ECMs. Obviously, it seems to have worked, so I learned something today. Just surprised.
[This message has been edited by Raydar (edited 12-10-2017).]
ECM Label Format change a bit over the years but 0122 might be correct. 86 might not be a year but prefix mean nothing for use here. Just scan will tell you.
Scanner may report Internal ID as 4 digits or break into 2 screens like ID hi and ID low. All scanner read but poor ones may ignore the field(s) in the data stream. that I seen IID have never used more then 0 - 9 for any GM OBD1 ECM w/ removable chips.
While External ID AKA Broadcast Code are unique codes... IID numbers may not be.
GM and some others likely has a list w/ both IDs + part numbers to order them, CA/Fed emission, etc. Standard made OE chips and updates but I think now discontinued this.
