Yeah I took it out and looked it over. Pulled it apart didnt see any broken welds but did notice that the cover had been slightly bent down ontop pressing against the board so Im figuring some shorting went on here. Ill probably send it out to be looked over and rebuilt if needed. In the meantime the people I bought the optispark from are gonna send me a new one. Im thinking should I even bother installing it in fear it might get burnt out or something. Yeah this is an electricle nightmare for sure. I am definitely going to hear this thing run though its not my nature to give up. I got time and I have another car so Ill go through all the procedures I need to. Is there anything particular I should be looking for other than broken welds on that box

Thanx

 

Oh and yeah wasnt such a stupid question after all. The aldl was up under the dash I had to pull down the carpet cover and plastic to find it sitting there. With hat I go to plug my scanner in and of course the batteries are completely dead. Yeah it can get like that but ya know what you keep movin on and oneday walla Im gonna fire this sucker up. Lets see how long this plays out it could get ugly. I just want to thank everyone who has helped me so far this is no easy task but man am I learning stuff here

Thanks

PS I hope my other buddy on here who is having such trouble with his vibration damper reaches the promise land and gets that sucker off. You got to be willing to suffer to own one of these cars thats for sure

 

question if I replace the ecu in the future will I need any reprogramming or will I be able to just plug it in. Also anyone know of any good places to get a new ecu at a good price or even get mine checked out and rebuilt

Mike

 

There is a forum sponsor that posts on occasion. They sell remanufactured PCMs or they can rebuild yours. The PCM is ready to go when you receive it, assuming you have a stock engine (ie you don't have a custom tune due to engine modifications).

The name of the company escapes me, but I bet if you put "need Rebuilt PCM" in the title of a new post you'll get a response.

 

some one might have had the panel off and forgot to bolt it up and just pushed it up there somewhere

 

Try www.autoecms.com

 

Thanks so much for the info. Ill check into the ecms. Id say that could very well be it but Ill take my time and test evertything I can before I go that rout and no its a sock setup no mods oh wait it has a 30 horsepower air foil add on forgot to mention that lol

So Im back home and headed out the door to work on the car and do some more testing. Im gonna test out the wires to the ecu to make sure they are solid with a continuity tester and a few other things who knows might get lucky. Ill post my findings as I go along, thanks again everyone who has posted to help me I rely on this site a lot. Id be lost without it

Mike
Long Island

 

did you search zip corvete

 

No offense man, but when I read the above quote, I did a major coffee spew !!! I was thinking to myself..."keep shaking the PCM and the damn car might just start up !!! Your problem sux though, and I feel your pain...

Anyway, here is something to check out. You need to have a high impedence DVM to do this:

(This is a cut/paste test procedure from unknown author. I did perform these tests on a working '94, and everything checks out, I made a video of these tests and can post on youtube....If I can locate the video I made last year...)

OPTI and Spark Test


The opti has two functions in the spark process. The first thing that happens is as the cam turns, the optical section of the optispark picks up the signals by the rotation of the shutter wheel. The pulses are sent to the PCM via the optispark electrical harness. The PCM processes the signals along with other sensor input and determines the proper time for the coil to fire. The PCM sends a signal to the Ignition Control Module (ICM) and it, in turn, causes the coil to fire. The spark from the coil travels through the coil wire back to the secondary ignition section of the optispark (cap and rotor), to be distributed to the proper cylinder.

If the opti is never sending the signal to the PCM, the PCM will never send a signal to fire the coil.

Here is some testing you can do. Refer to this diagram:
.

.
-Disconnect the ICM connector. Leave coil connected.
-Turn key to ON. (but do not start engine)
-Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM.
Result should be 10v dc or more on both terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad.
-If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire).
-If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM or any of the wiring in between. Visually inspect all the connections you can get to for poor contact or corrosion.

edited 5/16/2004


PS what does KOEO stand for ??????

 

Key On Engine Off

 

Hey there thank you so much
and I hear ya sorry that you had to waste that good sip of coffee lol
Ok KOEO stand for key on engine off. I have eliminated one potential issue and that is the wiring from the Optispark ( Harness ) all the way back to the ECM is all good. It all checked out with a continuity tester so Im sure there are no broken wires there and I also checked for the a/c signal wire from the ECM to the ICM and that checks out for continuity so I know one thing for sure there are no broken wires there at all. That checks out. I did the above test on the ICM once and got good voltage its when I checks for the a/c voltage that I got nothing and I was reading somewhere that it said suspect the ecm, Hmmmmmmmm?
Nevertheless Id love to check the opti itself like you mentioned with that video. Also what is a DVM meter and how much are they, I sure wish I had one. I have a pretty good metter just dont know if it is dvm. If you find that video please refer me to it. Im starting to narror it down I feel but Im gonna run a few more double checks. right now it can still be a few things but if I could eliminate that opti boy that would really help. I think it is the ecu but it could still be the ICM Opti or ECU. I do have an msd coil in there that is coming out. No need for it the ignition system is a high energy system and the coil isnt gonna do **** for it. You only put a 6a in a blown car and they say they are known to blow optis so its out and who knows I could get lucky on that either way Ill know it isnt the coil ( it was cheap enough also so ) In anycase please get back to me with what you find and if you find your vid and in reference to what a dvm is, thanks so much

Mike

 

Al Borman

Yeah in reference to taping on the ecu thats what I was hoping eventually it might start lol to funny and probably will. Im gonna get to the bottom of this before the year is out lol Thanks so much for the help and diagram. Im working it

 

DVM = Digital Volt Meter.

Any chance you have a friend with the same year car so you can borrow is PCM or whatever other things you might need for testing purposes? Years ago I found I had a bad ECM on a 86 by doing that.

Jake

 

Yeah, I was thinking that might help determine the root cause of your problem considerably.

I remember a couple of years ago (before I had a FSM) a buddy helped me determine a faulty ICM in my car by swapping out the one in his LT1 Camaro.

 

I saved this from a post a while back. Hope it helps...

How TO DETERMINE IF THE OPTI'S BAD

Check to see if you have a signal from the PCM to the ICM on the white wire. While someone cranks it over, check the white wire to ground for 1-4 volts on the AC scale. If that's there, the problem is between the ICM and the coil.

2 of the wires go from the ICM to the coil. With key ON engine OFF, those 2 wires have 12 volts on them. Find them and be sure they have 12 volts with the key on. One of the other 2 wires left goes to ground. Find it and confirm it goes to ground. The last wire left is the one that carries the control signal. It will test out as I said on the AC scale when someone cranks it with 1 to 4 volts AC. Also measure the resistance of the wires on the opti harness.

If you are getting 1-4 VAC on the white wire it means your opti is sending pulses to the PCM which is sending signals to the ICM to fire. Then your problem is not the PCM or harness. It would be ahead of that which leaves the ICM, coil, and opti.
http://shbox.com/1/95_ign_system_schematic.jpg (Diagram courtesy of Shoebox)

Disconnect the ICM connector. Leave the coil connected. Turn key ON engine OFF. Check for dc voltage at harness terminal "A" to ground and and also "D" to ground. You should get 10v dc or more on both terminals.

If you get no voltage then its the coil or ignition fuse.

If you have good voltage, switch the meter to AC and connect the leads to terminal "B" and ground. Watch the metre while someone cranks the engine. You should see between 1 and 4 VAC. If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM or any of the wiring in between.

Measure the resistance of your coil. If its around 5000 ohms or so its fine. Any higher than 7000 ohms means you should replace it. Measure the resistance of the opti harness and if it seems very high, replace it.

So then if your car passes all the above tests, its the opti.

 

Thanks everyone, No wish I had someone with the same year car as mine. This is an extremly difficult problem to identify for many reasons. I know over time Ill get to it and get it running. I was thinking maybe I put the opti on wrong but it slid on very nicely and snug. Im gonna check the ICM wires again and if Im not getting that a/c signal to the ICM which I wasnt getting last time Im gonna send the computer out to be repaired. There is a guy on ebay who does it pretty cheap and his feedback on them is very good. This seems to be the next best thing. I mean aside from everything else my scanner wont read from the obd1 port I get a message wont connect and I think this obd1 port is also linked to the pcm. Everything in my opinion points to the PCM in my opinion. Just wish there was a way to test the opti while on the car for signals being sent before it hits the PCM that would help me tremendously to rule out the opti. How would I use a dvm to measure the low high resolution or could i use a test light just to see if it sends pulses. Ok Im gong outside to do a little more testing. Holy God this is a hell of a Job

 

Ok just went outside and tested the ICM test again. I am getting good 12 volts to both wires so that checks out and I checked the white wire from the pcm to the ICM and I am getting between 2.5 and 2.8 A/C signal which means the PCM is sending the signal for the coil to fire. and the other white wire checks out good to ground. Does this mean its not the opti
Im wondering can the ICM be bad. I mean this means the icm is sending the message to the coil to fire and it isnt. I also just installed a new coil so it cant be the coil. I hope Im getting hotter now and closer to fixing this.

 

After chewing on this a bit I'm now wondering is swapping in a friend's PCM (as opposed to the ECM I swapped in) will work. I'm wondering if there's something to do with the VIN that would prevent that from working. I know it worked using my buddy's 86 ECM in my 86, but PCMs may be different somehow.

Anybody know?

Jake

 

Have you been to Shbox.com? Rob's posted procedures for testing the ICM, Opti and other things as well.

 

Mikes1991 - where do you live?
6spd or automatic?
If you are close to me and have a 6spd I could loan you my spare ECM to see if thats the problem.

Did you test out the cable from the opti to the passenger side intake (I know you checked some wires, just wondering if you checked this specific cable.

good luck.