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Discussion Starter · #1 ·
Hello all,

I am posting here because frankly I'm all out of ideas with this one. I have a 1994 Pontiac Firebird Formula with LT1/T56, Canada build. The car has always run great, I would consider it one of my more reliable machines normally. I went to start it about a week ago and it cranked fine but wouldn't fire up. I didn't really have time right then so I got in my other car and went on. When I got back home, the Firebird started right up. I took it for a drive and it was like nothing happened. It continued to run flawlessly for about two days, then suddenly it again cranked but refused to fire into life. At this point I had a few items in mind, and had ordered them just in case. I started with replacing my Opti Harness, when I did this it started right up, drove about a quarter mile and died like someone turned the key off. I waited about 15 minutes and it started back up so I took it home. It hasn't started since then. In totality, I've replaced the opti-harness, the ignition coil, the ICM, and checked all known grounds. The plugs and wires are fresh and undamaged. There are no codes stored in the PCM. VATS is not flashing and all of my dashlights come on when I turn the key to run. The only thing I found odd was that about a month ago I lost some of my dash backlighting, so I'm starting to think maybe the ignition switch? At this point, it seems like it could only be that, the Opti Spark itself or even possibly the PCM. I can't see why a PCM would just fail but the opti is not old and this one has never given me a fuss. Any thoughts appreciated, especially at this point!
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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How did you scan it for codes? There are codes for things that will shut down the engine (Opti, ICM), but do not turn on the SES light. If you don't have access to a compatible OBD-1 scanner, there is a free download of software on this site that will pull codes for the PCM, SRS, EBCM systems, and data log the engine.

Have you checked the fuel pressure?

Problems with the ignition switch are becoming more common. Typical problem is melted contacts at the harness connector. The first paragraph of this writeup may give some insight:

http://shbox.com/ignsw/ign_switch_repl.html

PCM failure is EXTREMELY rare.
 

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Discussion Starter · #3 ·
How did you scan it for codes? There are codes for things that will shut down the engine (Opti, ICM), but do not turn on the SES light. If you don't have access to a compatible OBD-1 scanner, there is a free download of software on this site that will pull codes for the PCM, SRS, EBCM systems, and data log the engine.

Have you checked the fuel pressure?

Problems with the ignition switch are becoming more common. Typical problem is melted contacts at the harness connector. The first paragraph of this writeup may give some insight:

http://shbox.com/ignsw/ign_switch_repl.html

PCM failure is EXTREMELY rare.
I use TunerPro via the ALDL port to scan for codes. I was shocked that absolutely nothing was stored. I have not admittedly checked fuel pressure but the pump does prime and fuel comes out of the valve. I will however acquire an actual gauge to verify its adequate. At this point I'm hoping its just the ignition switch, but I would think that would leave my with no cranking power either?
 

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"This Opti is not old" DOES NOT MATTER! ...especially if it's one of the cheap ones. I have never gotten more than 6,000mi out of a non-OEM Opti. I've been through them all. NAPA's, AutoZone's, Advance's, O'Reilly's, & Accel's. This last time I bought a "Delco" Opti from Summit Racing. It is the same re-man OEM Opti GM now sells for $920 with the same "factory" warranty. Time will tell on that one, but, I'm confident.

The Opti should throw a code for the high or low resolution pulse when one or the other fails, however, I had one with a bad ground. When the ground would "open" from thermal conditions, the engine would shut down without a code. There is a writeup of it here: http://www.firebirdnation.com/forums/topic/504089-93-firebird-optispark-failure-analysis/

Those auto-part-store Opti's are great for selling the vehicle. They are cheap and bet the vehicle running long enough for sale. They were built to a price point, not function. Seriously, look at them: the complete distributor is sold for *less* than they sell the "cap & rotor" kit for. How can that be good?

If you have one of the cheap Optisparks, even if it has a "lifetime" warranty, write it off now and get OEM. It is NOT fun replacing these things over-and-over-and-over-and-over. Eventually, the anti-freeze alone will top the cost of the cheap Opti. It's a losing bet at best.

You're right about ECM/PCM, it's rare for them to go bad. Very rare. Not saying it doesn't happen, it's just least likely.

I think this is the 94-97 Opti: http://www.summitracing.com/parts/ado-19212300/overview/ sure, twice the price of the others, half the price GM charges, 100 times less headaches.

Best of luck to you.
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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Unfortunately I have no experience at all with the TunerPro code scanning capabilities. In the 15 years or so I have been helping people interpret their LT1 data logs I don't think anyone has ever sent me one from TunerPro.

I think this is the 94-97 Opti: http://www.summitracing.com/parts/ado-19212300/overview/ sure, twice the price of the others, half the price GM charges, 100 times less headaches.

Best of luck to you.
The split on the Opti is 93/94 (unvented, shaft drive), 95-97 (vented, pin drive). His 94 is the same as your 93.
 

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The split on the Opti is 93/94 (unvented, shaft drive), 95-97 (vented, pin drive). His 94 is the same as your 93.
You got me on two points there: I was looking for the 95+ Opti for some stupid reason and it clearly states everywhere "1994". Also, I thought 94 was when they went vented/pin-drive. Always thought 92/93 Corvette and 93 fbody's were the only shaft-drive non-vented Opti. I stand corrected.

Summit Racing has it wrong, they list the one I linked as 1994-97 for fbody, yet, they also show the un-vented Opti as 94-94 on fbody, no mention of 1993 at all... I'll call them. Thank you.
 

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While the Opti is believed OEM I just went ahead and got one along with an ignition switch/harness and a fuel pump/filter. The previous owner did both the Opti and the fuel pump, while it hasn't given me any issues I have seen his crafty work so I'm just going to hope I open one of these up and find something interesting.

I looked around on the website, I couldn't find much regarding this scanning software. Could someone point me in the right direction on that?

I certainly don't think my PCM is the issue (or hope at this point) but would the fact that my computer communicates with it eliminate that suspect?

With the dash already coming apart at least I now don't have to do it twice. I've been meaning to replace my brake light switch, just wish the car was running to make it easier lol.

Is there anything else I'm missing? A classic suspect I haven't checked?

I've replaced the ICM/coil, checked all grounds in the engine bay. I'm going to pull my kick panels too just to check those, but I'm sure those rarely go being inside the car. I did finally get a pressure gauge on the car. Pressure was reading fine on inital prime and under cranking. I still ordered the pump because the existing one was changing pitch(relative to its normal noise) on occasion this winter.

I really do appreciate your time, this car has never given me such a headache!
 

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Scan9495 software by GaryDoug: http://www.firebirdnation.com/forums/topic/450959-scan9495-free-scanning-software-for-9495-lt1-obd-1/

You will need to buy or build a cable to use the software. Instructions on how to build a cable are located at the same link as the Scan9495 LT1 V8 files. Grab the PDF and Scan9495 LT1 V8 directory at the mediafire link and you'll have what you need sans cable. If you want to buy the cable, there are plenty of existing discussions on this forum covering that. I have no idea who to recommend there. GaryDoug's Scan9495 software though, you'll love it. ;)
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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Why are you taking the dash apart? For the ignition switch? There's an online procedure available that pulls the steering column.

What specific things are you looking for behind the kick panels?

Fuel pressure was "reading fine"? What were the numbers? How fast did it leak down when the pump shut off?
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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No crankshaft sensor on the 1994 LT1 V8. Everything is run off the optical cam position sensor in the Optispark distributor. That's why I asked about codes. DTC 16 for the low resolution signal shuts down the fuel system. Irregularities with the high resolution signal MAY set DTC 36.

There is a CKP on the 96/97 LT1 (OBD-2) system, but it is only there for misfire detection, and easy to access.
 

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Discussion Starter · #13 ·
I'm certainly not removing the entire dash, just really meant all of the panels under it plus the steering column. To my surprise there were no signs of burning whatsoever on the switch, I hear its pretty much normal after years of use but not here. It also cycles just fine, but I will still replace it since I went through the trouble. In reference to the kickpanels I really just wanted to check all of my grounds out. Reading fine in terms of fuel pressure meant about 42PSI under cranking, which seems like the normal to me. I didn't notice any leakdown but I really just let the thing prime and then put it against my windhshield so that I could see it while cranking. It held steady in those ~10 seconds.
 
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