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I have a 94 Firebird v-8 stock. It has been down since 2009 with me replacing and repairing only to find a vicious loop. I will try not to be wordy.

I ran out of coolant driving cross country (bad sensor), had a shop put in wrong coolant. Took out my waterpump, opti, serpetine belt. Replaced coolant switch, flushed radiator system, replaced waterpump & Opti. found PCM was unable to communicate or operate.

2010 replaced PCM had it recoded for upgrade to 160 thermostat, cleaned engine (opti is off good time to do) replace water pump (2) & opti (2), rewired harness (due to melted wires). I bought a second harness, checked all wires, rewrapped)

2011 Replaced both fans (new), replaced opti harnesss, replaced spark plugs & wires. another Opti & waterpump. Wouldn't start....replaced coil to msd, replaced ignition switch... still not running

2012 starter went out...replaced starter & changed oil to royal purple broke y pipe sat for 6 months more...

this month replaced fuel pump, cleaned tank, replaced fuel filter...coil bad replaced coil, replaced AIC, fixed exhaust (which is still smoking)

She runs (if you like loud) rough ...overheats fast...fans stopped working after 50 miles (neither engage even with AC)...has a clicking noise that appears to be coming from Opti (3), put it in drive and it bogs down with a shimmy as you excellerate.

Can my PCM (2) be bad again? My ERG was replaced 2009 before this began along with new o-2 sensors. Scan shows low AC coolant code 61 only. no lights stay on, takes second turnover to start first thing daily. I haven't checked my opti yet but i think it is going out again. What made my fans die? I have spark & fuel pressure seems ok (had a mechanic fix this week)

I need help before I go postal on this engine!
 

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I did have a green wire from passenger kick panel that was shorted over to the red grounding box. Don't know why because it wasn't in the spec (previous owner did), and I removed since i was rewiring the harness.

This car runs, but acts like it is shutting down. I can't drive without fans & overheating issues since 2009.
 

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Did you bleed the cooling system after replacing cooling system parts? shbox.com has pic of where bleeder screws are.

Pcm's rarely fail on these cars, chances of going bad are small.

Have you downloaded the 94 factory service manual found in this section. Look for thread titled "GM service manuals". Volume 2 is where, electrical section, driveability, and emissions are.

There is a handy pcm symptoms chart in the driveability section, that tells what symptoms you get when each wire of pcm is bad. Study that and rest of volume 2, as it has troubleshooting, wiring diagrams, etc.

You need to put car on a scanner that does codes and real time running sensor data. 3 big ignition codes 16, 41, & 42 don't light the check engine light and will keep car from running. Do a running sensor scan, it can tell you much, after studying the pdf I sent.

When you replaced the opti, did you buy one of the cheap Chinese ones. If yes then that could be your problem. But head to lt1 engine section and look in sticky threads for the diagnosing the optispark thread. Watch the video, run tests. Shoebox's site also has opti and coil testing.

If fans will run at all, hooked directly to power, then you should be able to hook up a manual fan switch to turn them on. Again look for instructions at shoebox's site.
 

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Of all the parts under the hood, the PCM (with NO moving parts) is the least likely thing to fail in normal use. I have one just like yours on a test rig and have accidentally shorted terminal pins many times over the last few months. Still going strong.
 
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