86 IROC Computer Help! - Team Camaro Tech
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post #1 of 10 (permalink) Old Mar 2nd, 03, 05:54 PM Thread Starter
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Does anyone know where i can get a computer for my 86 IROC? The Service Number is 1227165. Also what goes bad when a computer goes out?

Thanks, Mike
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post #2 of 10 (permalink) Old Mar 2nd, 03, 06:03 PM
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I would also replace the prom chip inside the pcm
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post #3 of 10 (permalink) Old Mar 2nd, 03, 06:09 PM Thread Starter
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Could you fill me in on the prom chip? I have no idea what it does. Also after i find my replacement ECM i wanna get one of those things that you can hook up a laptop to and read the cars performance.
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post #4 of 10 (permalink) Old Mar 3rd, 03, 05:25 AM
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Greetings TSP-MIKE,
You can find a replacement for that part number at NAPA, their part # is XTP647. The chevrolet dealership will also be able to get them for you. Also this computer part # is used in Iroc's up to 1989. I was able to find a good one at a local junkyard that also had a good chip in it. Also as a little side note if you decide to get the NAPA computer. The chevrolet dealership does not accept them as a core replacement if you ever go back to them for a computer. [img]graemlins/thumbsup.gif[/img]
I'm sorry I can't help you with the computer chip, for that particular year there were 10 different part #'s and 25 different codes for those chips. The part #'s and codes depended on such things as emissions, gear ratio, tires, & import/export status.

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[ 03-03-2003, 08:42 AM: Message edited by: trickster ]
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post #5 of 10 (permalink) Old Mar 3rd, 03, 02:35 PM
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As for what goes bad...it varies greatly. Possible failures include output driver failure (used to drive motors and solenoids), input modules get zapped (read various sensors and turn analog signals into digital values). PC boards can delaminate. Integrated circuits can fail. It's very difficult to troubleshoot a computer problem without a schematic or knowledge of the chips used.

The PROM is a programmable read only memory. The PROM is used to store the baseline control algorithm for a particular engine. The PROM is where the code is that gets tweaked by "performance chip makers". The PROM itself is very suceptable to electrostatic discharge. Also, the pins on the Integrated Circuit package of the PROM can get bent over.

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post #6 of 10 (permalink) Old Mar 4th, 03, 01:56 AM
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Unless the car got hit by lightning, it's very unlikely that the PROM would have failed along with the computer. I've been repairing computer controlled vehicles since the early 80's and I've only ever seen 1 PROM burned out. (and that car really did get hit by lightning!! ECM, PROM, Alternator, Radio and damn near every other electronic "black box" got torched!)

I wouldn't buy the PROM.

Don't replace the computer until you are sure that you have isolated the cause of the initial failure. If the car has a short in the wiring, or some similar failure, it is very possible that you could burn the new computer up before the car ever even starts! It gets very expensive in a hurry to troubleshoot by replacing parts. Find a factory service manual and a meter and "ring the harness out" from the ECM end before you pop in the new box.

Just my .02

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post #7 of 10 (permalink) Old Mar 4th, 03, 07:15 AM Thread Starter
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Well for a while now the idle just kept rising everytime i start the engine. Before it was just 1500rpm now it's at 3500 Rpm idle. Then i was told that the computer some how controls my transmission too. Since i was going 60MPH at 4500 Rpm in overdrive. The other day i cranked it up and tried to check my tps and iac. Well when i tried to turn it on again all the dash lights were out, and my car alarm didn't even work. I check all the fuses and they were fine. I tried to reset the ECM but that didn't work either. Yesterday i found a comp at the junkyard and installed it. everything came on again but it would not start. I pulled the chip off my old comp and stuck it in the new one. It cranked right up but didn't fix any of the problems i was having. I was messing around and plugged my old comp and the chip back in. It work too! So now i donno what is going on.

Thanks, mike
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post #8 of 10 (permalink) Old Mar 4th, 03, 09:05 AM
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When you had the problem where everything in the car was out, that was probably a loose of corroded battery terminal. There is no way that the computer could do that. The only thing on the dash it really controls is the check engine lamp.

The screamin' hi idle sounds more like a vacuum leak than an ECM problem to me.

On an '86 Camaro, I don't thinnk that the computer controls anything in the trans except for the torque converter clutch lock-up solenoid.
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post #9 of 10 (permalink) Old Mar 4th, 03, 09:36 AM Thread Starter
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When i said that all lights were out. I meant that on the dash all the lights were out. I could crank the car easily but i was getting no spark or fuel. The car was half working! I also have a sound system in the car and that half worked. The cd player would turn on but did not power up the amp.

For the high idle i tried spraying the intake manifolds and vacuum lines with carb spray when the engine was running. Didn't notice any idle drop. Is there another way to check for vacuum leak?

On the tranny i didn't think the computer had much to do with the trans exept what you said about the tcc. I tested that and it seems to be working. I drove 45mph and push the brakes alittle with the other foot and the rpms jumped up a bit.

Any other ideas?

Thanks, Mike
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post #10 of 10 (permalink) Old Mar 5th, 03, 01:34 AM
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With the info given by dnult, Pdquick & the trickster, damn good info, by the way, my 2 cents is this:

The PROM is protected by its controller. The controller does just that , controls everything by instruction/decision from the PROM. Whatever controller you use, (must have the same part number as orig), I suggest to start from ground zero.

Clean battery posts and clamps. Clean ground connections. Make sure the alt BAT wire is in good shape. Now, since you've cleaned, ECM memory should be dumped and clean. So now you can start over with the troubleshooting process.

Start the car, let it warm up to operating temp and let it run alittle longer, maybe even takeit for a 4-6 mile cruise. Come back to the driveway and if its still revving, look for a vacuum leak, carb cleaner, WD-40, etc will work. Check hoses, brake master vac, A/C vacuum line going into the firewall, PCV valve & its hose, you get the idea. Make sure the intake track, hoses, are in good order, no holes or splits from the air scoop thru the AFM 9if equipped) to the throttle plates.

If no vacuum leaks found, then with key off, jumper the ALDL connector pins A to B. Turn key to ign, engine off. Several events will happen.
1. Codes will appear at CHECK ENGINE light, look for Code 12, i.e., pause flash pause flash flash pause. This code suggests ECM can communicate. Other codes will appear in their order. Copy them down. Then ECM will repeat codes.
2. IAC motor seats itself to plug the air hole in Throttle body.
3. EGR solenoid energizes to allow a vacuum pump, such as a hand pump, to test and open the EGR valve. This checks the diapharm, but not the seat/needle on the exhaust side.
4. Cannister solenoid energizes for purging of same.
5. After t/s, don't forget to turn off ign and remove jumper.

The above checks the controller side of the ECM. Getting back to the codes, when one looks up a code definition, it gives an area to look into. It might be its control side is hosed, broken wire from ECM to the device, or device itself is bad. Or control side may work fine, but, the function side is hosed, such as an EGR valve, it moves up & down, but there is dirt or a hole on the needle and seat keeping it open to produce a vacuum leak.

Just try keep your thoughts straight when troubleshooting. If you have a TPI equipped engine, it mif=ght be the EGR valve malfunctioned. I have read its a pain to get replaced.

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