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Old 02-25-2013, 11:37 PM   #1
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Default Engine stalling

Hey guys, I need help. I have a 94 trans am that just started stalling on me. I already changed out the ICM twice today. The first time I changed it, it still died when it got warm so I took the ICM back to exchange it for another one and that one worked better. With the second one, I was able to let the car idle for 30min then drive 8 miles to get home and everything was fine. I let the car sit for an hour, then when I tried to drive it, it stalled 2blocks away. I have a spare coil so I'm going to try to put that on tomorrow. Is there a way to know for sure if its the ICM? Also, this morning while driving the rpm's would drop from 2000 to 500 for a few seconds then go back. It did that about 3 or 4 times. Anybody have any suggestions?
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Old 02-26-2013, 12:09 AM   #2
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Originally Posted by eDD_z28 View Post
Hey guys, I need help. I have a 94 trans am that just started stalling on me. I already changed out the ICM twice today. The first time I changed it, it still died when it got warm so I took the ICM back to exchange it for another one and that one worked better. With the second one, I was able to let the car idle for 30min then drive 8 miles to get home and everything was fine. I let the car sit for an hour, then when I tried to drive it, it stalled 2blocks away. I have a spare coil so I'm going to try to put that on tomorrow. Is there a way to know for sure if its the ICM? Also, this morning while driving the rpm's would drop from 2000 to 500 for a few seconds then go back. It did that about 3 or 4 times. Anybody have any suggestions?
have you scanned it? sounds like a bad sensor since its only happens when it warms up
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Old 02-26-2013, 12:15 AM   #3
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I might scan it tomorrow. It might also be that it's an autozone ICM
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Old 02-26-2013, 06:46 AM   #4
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Did you put heat sink compound on the back of icm and on heat sink. Same stuff used on your pc processor. If not, the icm can burn out quickly.

As screaminZ suggested, a scan is in order here. Not just a code scan, there could be some silent codes that don't light the ses. But also you need to use a scanner that does real time sensor data scans. Many times you can catch a sensor that is not working correctly.

Iac is a suspect if it stalls when coming to a stop. Scanner should tell you what most sensors are doing. If you don't know how to interpret sensor readings, pm me with your e-mail address and I'll send you the pdf file of "scanner readings and what they mean".

Back to the codes. Ignition system has 3 silent codes that will shut car off. Dtc 16- opti low resolution pulse missing, and dtc 41, 42 both icm related codes and all 3 don't light the ses light.

Finally, you will need a scanner that does obd1, that's what your 94 is. Unfortunately, companies don't make obd1 only scanners anymore. You would have to get an obd1 & obd2 combo scanner to do the job. They are kinda pricey.

I suggest the actron CP9145 super scanner. You can usually find it on ebay or amazon for around $140. Because your 94 uses the GM obd1 12 pin dlc, you would also have to order the cp9127 GM 12 pin dlc adaptor for around $35

Another option for your 94 would be to turn your laptop into a scan tool. Get a cable that hooks up your car's dlc to usb port of laptop. Get at www.aldlcable.com $59 plus shipping.

Then get program called DataMaster EE it will scan for codes, do running sensor scans, and log data to a file that can be played back in real time. Available as a trial version good for 20 free scans and unlimited data playback at www.tunercat.com

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Old 02-26-2013, 06:56 AM   #5
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Autozone and other parts stores usually can't scan obd1 cars.
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Old 02-26-2013, 08:42 AM   #6
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Yes I put the heat sink compound. I have the tunercats cable, so I'll try to scan it with freescan and datamaster
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Old 02-26-2013, 01:30 PM   #7
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Scanned it, codes 16, 48, 41, and 50 popped up. Erased the codes, turned the car on and it shut off once it warmed up to 190. No codes popped back up. Fired it back up 5 minutes later, let it run for another 30 min. Temp went over 210 without shuting off. Still no codes. I don't really know what to look for now
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Old 02-26-2013, 04:33 PM   #8
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i tested the icm and opti harnesses how it says on shbox.com 4th Gen LT1 F-body Tech Articles
everything tested out fine
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Old 02-26-2013, 06:14 PM   #9
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can you run a datalog until it dies and post it?

while it's still in a 'wont start' condition, can you pull a rail, put a spark tester on the coil lead, and crank it, to see if you're missing spark, fuel, or both?
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Old 03-03-2013, 11:43 AM   #10
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It was the opti
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