It has been suggested that I replace the ECM on my 86. Is there a test that can be done that will prove it is the answer to my problem? It seems like I have tried everything else, the only thing left is the ECM, but I don't want to be guilty of being a parts hanger.

When I read through these threads about cars with the same symptoms as mine I do not find where anyone reports if their car eventually got repaired or what the final cure was. Why is that, aren't they getting fixed?

I was having a problem with my 87.It would run good then choke out and so on and so on! After about 3 weeks of pissing around with it the only thing I had not changed was the ecm and prom. $250 later at the chevy dealership its running like a raped Ape! The only way i can figure to test it is hook a scanner up to it and see if it gets communication with your computer. If it says it cant establish communictaion your computer is probly jacked. Also when you first turn your ignition key to the on position the check engine light should illuminate for 5 secs then turn off. If it doesnt come on at all that may be a sign as well!

A bad Ecm with throw its own code. Whats the problem with your car?

The ecm was replaced in mine for this reason.

A bad Ecm with throw its own code. Not always.

Generally, you test everything else, and then and "Diagnose" the ECM by process of elimination. After you've diagnosed the harness, sensors and mechaincal systems as working correctly, the ECM is the only thing it can be.

Diagnose everything several times to make SURE you're not missing something before spending $$$ on an ECM. Last case I had like this it was for the CCM (equally likely to go bad -not very). It was down to either the CCM was bad, or the car had the wrong key (resistor pellet). I had confirmed that the ECM was fine, all invloved harness were niether open nor grounded, Etc. Everything checked out, per the FSM. And how could the car possibly have the wrong key?? I was ready to replace the CCM but decided to buy a variable resistor from Radio Shack and try all of the 15 different key resistor values first. On the second try, car started. Car had the wrong key.

Like Corvette Mike asked; What are the symptoms?

Symptoms? After dealing with my C4 for about 3 to 4 years sputtering and lots of research I finally found out (right before replacing the ECM) that there are two electrical thingees (power/burnoff relays) right behind the battery on an 87. They are little black cylinders attached to the firewall. It was suggested to me that they be replaced - I did and the problem was gone till I sold the Vette. The two electrical parts were $9.95 a piece.

Given the problems you have had and your time spent doing diagnostics , if you think it is the ECM at fault then you can get a used 1227165 around the Forums for $50 or less.
One sold on 3rd Gen yesterday for $20
Might be worth the $$ just to prove a point; if it doesn't work you can always resell it.
The memcal (chip ) in the ECM itself might also be at fault

Given the problems you have had and your time spent doing diagnostics , if you think it is the ECM at fault then you can get a used 1227165 around the Forums for $50 or less.
One sold on 3rd Gen yesterday for $20
Might be worth the $$ just to prove a point; if it doesn't work you can always resell it.
The memcal (chip ) in the ECM itself might also be at fault

I found one at Ecklers for about 100.00 but until I was certain I had ruled out all of the possibilities with my old one I did not want to order one. If you look at my posting about 86 runs and dies, you will see everything that I have tried. I haven't gotten much response lately on that post, so I think I am on my own from here. Thanks for your help

Not always.

Generally, you test everything else, and then and "Diagnose" the ECM by process of elimination. After you've diagnosed the harness, sensors and mechaincal systems as working correctly, the ECM is the only thing it can be.

Diagnose everything several times to make SURE you're not missing something before spending $$$ on an ECM. Last case I had like this it was for the CCM (equally likely to go bad -not very). It was down to either the CCM was bad, or the car had the wrong key (resistor pellet). I had confirmed that the ECM was fine, all invloved harness were niether open nor grounded, Etc. Everything checked out, per the FSM. And how could the car possibly have the wrong key?? I was ready to replace the CCM but decided to buy a variable resistor from Radio Shack and try all of the 15 different key resistor values first. On the second try, car started. Car had the wrong key.

Like Corvette Mike asked; What are the symptoms?

Take a look at my post a little farther down "86 runs and dies" I have tried everything with that car and wanted to be sure before I bought new ECM that it was the problem.
Thanks for the help

you will see everything that I have tried. I haven't gotten much response lately on that post, so I think I am on my own from here.
Done my head in thinking of possibilites. You have done a good diagnostic of the common problems with no result so it is tending to look like a ECM problem.

Done my head in thinking of possibilites. You have done a good diagnostic of the common problems with no result so it is tending to look like a ECM problem.

I tested the power at the ECM connections with a volt meter. I will try to paste the results here. Hopefully they will fit this page, I wrote it up in MS word.
Voltage on ECM plug taken from the backside of the plug using a paperclip as a probe and testing to a seat bolt for ground.

Key on

S/B POST S/B Post
0 A1 0 v Fuel pump relay B+ B1 12.45 v Battery
B+ A2 .32 v Air Switch 0 B2 .10 v Fuel pump signal
B+ A3 .33 v Canister purge control 0 B3 0 EST reference low
B+ A4 .33 v EGR control B4 Not used
0 A5 12.21 v Serv Eng Soon control 0 B5 .03 v Distributor reference
B+ A6 12.32 v Ignition 2.5 B6 .22 v VATS
B+ A7 .83 v Man trans O/ride 9.2 B7 8.5 v ESC signal
2-5v A8 .14 v Serial data B8 .02 v A/C signal
5 A9 .42 v Diag Term B9 Not used
A10 Speed Sensor signal B10 Park/nuetral
0 A11 0 Analog grnd MAF sensor B11 Not used
0 A12 Tone System ground 2.5 B12 .40 v MAF sensor input

B+ C1 12.21 v Fan relay control 0 D1 Tone System ground
B+ C2 .26 v Air control 0 D2 Tone TPS, CTS, MAT 5v return
C3 Not used 0 D3 Tone System ground
C4 Not used 0 D4 .32 EST control
C5 Not used 0 D5 0 Bypass
C6 Not used 0 D6 Tone Ground O2 sensor
B+ C7 11.97 v O drive switch signal .45 D7 1.75 v O2 sensor signal
B+ C8 0 M/T O.D. request D8 Not used
C9 Not used D9 Not used
C10 Not tested 0 D10 Tone System Ground
C11 Not used 0 D11 A/C pressure switch
C12 MAT signal B+ D12 12.2 MAF burn off relay cont
.54-.7 C13 0 TPS signal D13 Not used
5 C14 .01 TPS 5 volt reference D14 Not used
B+ C15 11.98 v EGR diag switch B+ D15 11.4 v Inj 1,3,5,7
B+ C16 12.41 v Battery B+ D16 11.68 v Inj 2,4,6,8

Sorry it doesn't lay out the same logical way that I wrote it. If anybody is interested the contact posts all have the letter and number of the contact post to the left of that post is what the book says should be "S/B" and to the right of the contact post and letter is what my ECM tested at.

Thanks for all of the help.
I tried an ignition module which did not help, so then I replaced the ECM and it started right up. Now onto the rest of the restore project.
Thanks again!