My black 96 Firebird that I bought on Halloween day in 2001 just died on the PA Turnpike tonight. Again.

It was stumbling a little bit at about 1800 rpm just before it just shut off completely, and I coasted to the edge of the highway.

The starter cranks but the engine won't start up. Battery gauge is down in the orange stripes where it just doesn't have enough juice to start.

I had it towed by AAA to my neighbor's shop where I had just picked it up this morning after getting it inspected. 13 miles. Lucky 13 the tow truck guy says. Crazy.

It was showing P0303 when I scanned it this morning. I figured maybe just a plug wire, no problem. It was stumbling a little at idle (about 900rpm) and popping through the exhaust at stoplights.

I cleared that code and it seemed okay when I left work tonight. About 35 minutes into the 45 minute ride home, the stumbling started and then all of a sudden, it just shut off.

Now normally this wouldn't be a big deal, but the exact same thing happened to me back in June.

I had a P0306 misfire that would not go away even after multiple plug and wire changes, so in June I replaced:
-The leaky water pump with an electric one from Summit
-The Stock Oil filled Optispark with an ACDelco GM opti from Summit
-The Optispark harness since the stocker was fried and missing chunks of insulation
-Timing set since I pulled the water pump gear drive and plugged the timing cover(timing chain was stretched and was off a tooth)
-All the front cover seals

I put it all together obsessively, including perfect dot to dot on the timing set, indexing the optispark in the correct drive slot,and the car ran great. For a day. I drove it to work and then on the way home,it just died in the exact same way that it did tonight.
It cranked but would not start.

The first time, I got it towed home and then I went down the list troubleshooting everything. Didn't want to just toss parts at it, right?
It got down to the GM Opti from Summit being bad because there were no signals coming from it.
I pulled it and the shaft was wobbling enough to let the signal wheel rub the sensor. I thought, it's brand new from Summit, how can it be bad? I was floored.

I was pretty fried at that point, so I went to AutoZone and picked up an Optispark from them. Nice and smooth, no wobble, everything spun nicely. Threadlock on the rotor screws. I put the AutoZone Optispark on in the same obsessive manner, making sure the correct index slot matched the dowel.

Right about then, I fried the starter and battery cranking the thing while I tested stuff with a VOM.
I got the alternator and the coil tested at Autozone and they passed.
I replaced loose metri-pack connectors and bad grounds at the coil and at the ICM.
Solder and shrink tubing all the way.
The fuel pump would prime at the jumper. Fuel pressure was 20psi, so I picked up a fuel pump at Summit, just in case. I found and fixed a sloppy fuse socket at the ignition fuse, (tricky because it read correct voltage on top, but on the bottom side of the fuse box, it was dead on one side) and it finally started right up. Fuel pressure went up to 37ish psi. I figured it's running so, it must be okay.

Took it for a couple of long shakedown runs where I babied it. It was running really smooth without the gear for the water pump on there and the temps were steady at about 190ish on the dash gauge.

Got it inspected, it was all good until it died tonight. I'm going to let my neighbor look at it. I figure a fresh set of eyes will figure out what my blind eye is missing. Maybe I'll get lucky and its something dumb and cheap.


I've been working on cars since I was 8 years old, 30 years, and I've never seen anything like these optispark distributors. I mean, it's just nuts that this 300 dollar part frags itself so easy. How do you get one that won't blow up? It's like a shell game with hand grenades.

 

Do you know the history behind the engine? A cam dowel pin that's too long can tear up some optis. I have never had a problem with an opti in 140K.

 

That first post was right after I got home from the tow truck ride so it was pretty heavy on the rant side, I apologize.

I've had it since 2001. Second owner. 30k on the clock when I got it. 118k now.

I don't think it was touched before I got it. I think the original owner got rid of it because it had the intake manifold leak.


I got that fixed and it ran great until I started getting the misfires.
I looked and the water pump had let go, and the seals had let go so I figured I would replace it all when I was in there.

Now I'm thinking the misfires were the result of the timing chain getting stretched, and I think that happened when the clutch disk let go mid shift (3-4th gear) getting on the highway about 2 years ago.

Now that I've had a couple hours to sit and think about it-

I've never actually gotten any of the codes for the opti being bad, I assumed the oil killed the sensor. I always got misfire codes. I replaced plugs and wires 3 times so I figured it had to be the opti. Now that's got me thinking that the stock opti probably just needed cleaned up.

speedygonzales, I think you are probably right. I've searched and used many of your posts as starting points when I've been at the "what the heck do I do now" points.

Bear with me as I mash my head against the wall like a complete idiot:

I never measured the dowel pin, and it just hit me that the aluminum backing cases of each optispark all have had visibly different thicknesses, the thickest being the stocker, the thinnest being the AutoZone replacement. The thin case would bolt up tighter to the block, and shove the dowel into the opti deeper. This would eventually push the shaft off center, frag the shaft bearing and wreck the sensor disk into the sensor and that in turn would kill the signal to the PCM and shut the car down.

I'm thinking that if this Auto Zone opti has a wobbly shaft, I've found my answer.

Can you shim the case off the block or do you have to remove the dowel and correct the length?

 

I would just put in the correct length dowel pin instead of messing with shiming things. Maybe even take a dremel tool and grind it down a bit? Idk kinda up to you.

 

Are you still pulling misfire codes after all those fixes? Sounds like the first thing that happened was your timing chain gave up and shredded everything in its path. Now, I think you give too much credit to the opti's bad reputation. I have an Autozone opti in mine with a MSD cap, and no problems yet in 10K. If you aren't pulling any codes and the car just dies, check your ICM. It will kill the engine when it gets hot, with no codes.

 

After I got the Autozone opti installed, it was like a brand new car.

It ran great for about 3 or 4 days.

When it died I got the same 2 codes I always got.
P0300, P0303 or P0306. Misfire codes. Stumbles. A pop in the exhaust at idle.

I've never gotten the low or hi res opti signal failure codes, but the opti is failing mechanically.

What I'm thinking now is:
-the dowel pin is probably the right length
-the opti shaft mounts fine on the end of the cam

-the replacement backing plate that the shaft bearing mounts into is slightly thinner than the stock one, it bolts up a little tighter to the block and puts just enough pressure on the opti shaft bearing so that it fails. Like the cam is trying to press the shaft bearing out the front of the opti, if that makes sense.

Maybe the optical sensor is fine, but the shaft is driving the signal disk into the sensor and its getting a goofed signal from that and that's where it shuts the car off

I'm not knocking the stock optispark, I'm knocking the quality of the replacement parts.

The first replacement optispark before the Autozone opti was a stock GM AC Delco part. I have a stock cam. Stock dowel pin. That was the correct length dowel pin for a stock cam and a stock opti replacement.

That sucker should bolt up perfect and not have failed, right? Do the GM techs pull out a micrometer when they change these things? We're not talking NASA rocket science clearances here, right?

These things should bolt on the same way any replacement alternator does. You know it will just bolt up because it is the correct part for the application. That's the part that drives me nuts.

the timing chain didn't break or shred anything, it stretched enough to let the crank gear get off 1 tooth.

 

I've heard stories of new optis that turned out to be crap, so maybe that's what you got. If you plan on changing the opti again, look into the MSD unit. $500 bucks, but you get what you pay for from what I've heard. The only other thing I could think of would be burned plug wires, or maybe you switched a few. I'm sure you already checked that, seems like you know what you're doing. I've had this misfire thing twice now so I know how you feel .