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I purchased my 94 Z28 about a year ago, after about 4 months of daily driving it I noticed the car would shut off randomly. I replaced the ICM with an ACDelco and ignition coil with an MSD. After a while I noticed a pattern to the cars bs. Initially starting the car after its cooled off it will go seemingly forever. Once I shut it down and start it back up, it will either crank and not start, or it will run fine for 60 seconds and shut off. Crank but no start. Usually after about a minute it will start again and run without an issue. Sometimes It will continue to die and not start until I let it sit for at least a few hours. It never sputters runs rough, but sometimes I can see it try to shut off when it usually would but jump back up to idle. I havent replaced the opti, but from what I've read it doesnt seem like that is my issue, and I'd rather have some insight before I start dumping money into it. I think It could be some sensor, or maybe a security issue. If anyone has a similar issue or any clue what I should look for please let me know. I can replace parts but I'm not great at diagnosing problems. Also im on a students budget :confused:
 

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You need a fuel pressure tester. First see if you have around 43 psi at key on prime. Tape gauge to windshield and drive car. Except for idle fuel pressure should be around 40 psi. At idle it can be in mid to low 30's psi.

When car does not want to run, see if fuel pressure has fallen.

Next, because car won't start hot you need an obd 1 scanner that checks for codes & does sensor scans. Many times a malfunction coolant temp sensor, the one on the water pump, engine won;'t start or will run a short time. The sensor scan will show the temp being reported to pcm by cts is way off from actuak temp of coolant.

And check for codes as there are codes that don't light the cel. Like tc 41 &42, which are icm codes. And dtc 16 which is an opti low resolution pulse missing code. Optical sensor in opti can fail when hot. As can icm. Did you apply heat sink compound to new icm you installed?

If no, icm can burn out or malfunction quickly. If you wish to fix your car, you need to learn trouble shooting. Go to the following link to download the factor 95 service manual. It has all sorts of useful info. www.mediafire.com/?40mfgeoe4ctti
 

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Yes the ICM came with thermal compound. I have a fuel pressure tester somewhere that I can find. My OBD scanner doesn't work on my Camaro for some reason. Do I need a special scanner for a 94?
Thanks.
 

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All cars prior to 1996 were obd 1 and most scanners sold in the last 10 years are obd 2 only.
If you go to the following link you can download the PC based obd 1 scan program called "scan9495". It was written by our member garydoug just for our 93-95 f-bodies. www.mediafire.com/?0elo4c935uc5s

Get the newest version in the lt1 v8 folder. To use the program you will need to download Microsoft dot net framework version v4 or newer. You will find it in a folder on same page as scan9495. Or get it at Microsoft site.

You will also need an obd 1 GM type 12 pin aldl to usb port cable. Get it at the following link.
www.obd2allinone.com/aldl.asp

When you get scan9495 up & running, you'll find you can scan for regular codes, as well as ABS & SIR codes. It will do running sensor scans and log data to a file so you can view it later on.
 
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