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Discussion Starter · #1 ·
This is my first post here.

Step-son has a 1994 Trans Am with ~78,000 miles. Recently it has been having trouble starting, or not starting at all (by that I mean it cranks fine, but won’t fire). I tested the fuel pressure which was 36# at idle (43 with regulator unplugged), and it stayed in the mid 30s at all RPM. I know that’s low, but it didn’t have any issues running rough. After testing the fuel pressure I took it for a drive with the regulator unplugged. Went WOT, and it died when it hit second gear. After that it would not restart for a few hours. Replaced the ICM, and the car started. He drove it to work, but wouldn’t restart after sitting for a few hours. It has been getting worse as the weather is getting warmer. He drove it all winter, so the moisture doesn’t seem to effect it. Any good ideas of easy fixes before changing a fuel pump, or (gasp) opti? Hate to just throw parts at it when he’s on a teenage budget. Like I said it never ran rough or had a miss, just dies. Has a new alternator and Optima yellow top, so that’s not an issue.
Thank you
 

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Discussion Starter · #2 ·
New coil didn’t work. I misted some starting fluid in the intake while cranking, and got no response. Must be an ignition issue, so all that would leave is the opti I think?
 

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A quick spark test on the coil output wire will confirm it's ignition; recheck the fuel since fuel pressure can test ok in the driveway but be bad under load or an intermittent. If ignition, there can be other wiring issues causing a problem beside the opti. Are you getting any trouble codes? Detailed troubleshooting is provided in the factory service manual at www.mediafire.com/?40mfgeoe4ctti Hard start is in Section 6E3-B, and ignition diagnostics are in Section 6E3-C4. The FSM gives you a path for checking the rest of ignition wiring before getting to an opti replacement. The opti harness is something else you can check.
Hope this helps -
Jim
 

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Did you put thermo heat sink compound on back of new ICM & it's heat sink? If no, your new ICM could be toast. Take ICM to auto parts store and have it tested. Make them run multiple tests to get it good and hot. That is when ICM likes to fail.

Attach your fuel pressure gauge to fuel rail, and tape gauge to windshield. Take car for a drive. Watch fuel pressure. When car dies see if fuel pressure drops right before engine quits.

If you replace op[ti, make sure you buy GM, Delco, or Delphi opti. The rest are junk. And buy a PC based oscilloscope for around $70 on Ebay, Amazon, etc. It is the only 100% way to monitor the low & high resolution pulse that opti sends to PCM. They should be well formed square waves with no drop out or changes in waveform.

If you have opti code 16 or ICM codes 41 & 42, the check engine light does not light. But PCM prevents fuel injectors from opening & disables ignition also.

Finally, go to shoebox site and read up on vats security system. It can leave your car non functioning. www.shbox.com

Oscilloscope is also good for reading the 50 hertz fuel enable signal that theft deterrent module ( TDM ) sends to PCM so PCM will open fuel injectors.
 

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Discussion Starter · #5 ·
I haven’t tried to check the codes yet. I put the new ICM on with some washers to keep it a little cooler. Unfortunately we don’t have a parts store that’ll check an ICM in our small town.
 

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This is my first post here.

Step-son has a 1994 Trans Am with ~78,000 miles. Recently it has been having trouble starting, or not starting at all (by that I mean it cranks fine, but won’t fire). I tested the fuel pressure which was 36# at idle (43 with regulator unplugged), and it stayed in the mid 30s at all RPM. I know that’s low, but it didn’t have any issues running rough. After testing the fuel pressure I took it for a drive with the regulator unplugged. Went WOT, and it died when it hit second gear. After that it would not restart for a few hours. Replaced the ICM, and the car started. He drove it to work, but wouldn’t restart after sitting for a few hours. It has been getting worse as the weather is getting warmer. He drove it all winter, so the moisture doesn’t seem to effect it. Any good ideas of easy fixes before changing a fuel pump, or (gasp) opti? Hate to just throw parts at it when he’s on a teenage budget. Like I said it never ran rough or had a miss, just dies. Has a new alternator and Optima yellow top, so that’s not an issue.
Thank you
I had similar issues and did all the recommendations posted here. Mine was a bad opti and a stopped up catalytic converter. Runs better than ever now after replacing the opti, plugs, and wires and removing the converter. ‘94 Trans Am 86,000 miles
 

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This is my first post here.

Step-son has a 1994 Trans Am with ~78,000 miles. Recently it has been having trouble starting, or not starting at all (by that I mean it cranks fine, but won’t fire). I tested the fuel pressure which was 36# at idle (43 with regulator unplugged), and it stayed in the mid 30s at all RPM. I know that’s low, but it didn’t have any issues running rough. After testing the fuel pressure I took it for a drive with the regulator unplugged. Went WOT, and it died when it hit second gear. After that it would not restart for a few hours. Replaced the ICM, and the car started. He drove it to work, but wouldn’t restart after sitting for a few hours. It has been getting worse as the weather is getting warmer. He drove it all winter, so the moisture doesn’t seem to effect it. Any good ideas of easy fixes before changing a fuel pump, or (gasp) opti? Hate to just throw parts at it when he’s on a teenage budget. Like I said it never ran rough or had a miss, just dies. Has a new alternator and Optima yellow top, so that’s not an issue.
Thank you
If the security light blinking after it shuts off try opening the door and check if the security light is blinking if so it could be the Vats vehicle anti-theft system I have a C4 Corvette and I put the bypass chip in for the but my votes system is still armed so I will have to buy the bypass chip
32628
 

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Discussion Starter · #9 ·
If we were swap in a regular SBC with, say, Holley Sniper fuel injection would the rest of the car function normally? Gauges, transmission and such? Are are there some sort of computer tuning modifications that need to be done?
 
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