it's one of the wiring components I'd considered, but I'd think that since it's a positive side deal that if that was it then you'd see a voltage drop at the time of the miss.

You don't have an MSD box do you? I've seen them fail this way as well.

Just grasping at straws and stuff.
-jeff

 

I have not actually scanned for a voltage drop, but the lights do dim a bit when the miss hits.

No MSD box. Like I mentioned at the first of the post it even did it with the LTCC conversion, plus I'm on my 3rd opti since the problem began, so it must be something else in the system.

About 18 mos ago I lost my turn signals...changed bulbs and stuff and ended up being the harness connector was coming apart under the dash, had to drop the column to get to it. It is plausible that dropping the column caused the ignition switch harness to losen, or its doing it on its own....easy enough to inspect though.

 

Have you tried swapping injectors?

 

Yup... been there done that. We swapped out the SVO 30s and put the stocker 24 # ones. That did absolutely nothing. So we put the 30s back in.

 

You might try swapping injector wires (like 5 and 7) to see if the problem moves. I wouldn't want to run like that for a long time but it should be ok to test things out.

 

Well, they are numbered so you can't get them wrong, but I swapped those two last night just on a whim and it made it worse because then both were missing.

What I can't figure out is why before it seemed more random and now it seems almost entirely the #7 cylinder. It was almost totally dead again tonight and has been since the opti swap this weekend.

Every option has been exhausted except the ign switch, but I won't be able to get to that till the weekend. Unlikely it could cause an isolated cylinder to miss, but it would account for a random miss.

 

I worked in the Electronics field in the past and this problem sure sounds like a intermitent short circuit to me.

the lights would flicker when the shortcircuit occurrs due to the instantaneous extra load. then go away due to the voltage dropping to a level where no "arcing" occurs. When the voltage goes up again the arcing will eventually happen again.

movement on a rusted conection could make it happen too. Now I am not expert in LT1 problems so I will in my own logic way diagnose it as an electrical problem and because of its nature I would diagnose some arching inside the optyspark or the Coil or along those lines.

If that is not the case maybe some problem at the alternator coils. Can you monitor the Alternator Voltage and Load at the same time? If you could then you could also rule out Short Circuit as it would not show as Alternator/battery Load. Remember your battery acts as a buffer so even if the Alternator is acting erratically the battery would dampen the voltage drop anyway.

Once again Loose wire to PCM or other main voltage feed to the electronics or voltage arching somewhere in the ignition system.

I hope I am right.

Marvin

Oh one more thought. Disconect your Alternator (electronically) and then see if the problem continues. Track the voltage at the battery at the same time checking for voltage variations with the alternator off. if the flickering continues rule out alternator/regulator completely and move to ignition. Gosh I remember my good old days. do not give up. be a detective here and better yet do not replace parts before you completely sure you got the problem pimpointed.

 

We will see if you are Marvin, because the car is going in to a specialist mechanic Thursday evening for a few days of diagnosis.

Alternator problems are a possibility, I put new guts in it a year ago w/o any change in the problem, but that's not to say it isn't something charging-system related. The entire ignition system is new except for the ign switch. No visible signs of arcing anywhere. Chassis and power grounds confirmed good & tight.

 

Chris possibly a PCM related problem dropping a ground to fire an injector, or also a compression/valve related problem. Have you ever check compression with all spark plugs out and the throttle blocked wide open? Just shooting out another idea.

 

Compression tests out at 195-210 PSI. THe injector harnesses have all been tested with a noid light. PCM has also been replaced (then swapped back when it didn't help). This has all been mentioned in this thread earlier...not flaming though because I know it is a long thread and its easy to miss details.

 

Got the car back from the specialist and unfortunately I do not have good news.

He scanned for missfires and didn't see any,which is obvious because I have missfire detection turned off in the PCM (which I told him), so there are no codes or miss counts.

To me, owning the car, its very obvious just by feel that it misses. Bill believed it was all cam lope however. He couldn't account for the significant vibrations at 1600 rpm in park though.

He also put the car on the "scope" and analyzed the wave patterns of each cylinder firing. He said all 8 looked extremely similar with very little deviation, and that he plotted them on a histogram and didn't see any changes over time.

So he says flat out its not missing. I still want to pull that ign switch, but if what he is saying is accurate, there is nothing wrong with the ignition system.

I don't think I am getting full voltage through the ignition though. If it was fluctuating the histogram would have shown it. But if ignition volts are just permanently low, then the spark may not always be strong enough to jump the gap and ignite the mixture.

No way it is not missing though, its pretty obvious some cylinders, particularly #7, are not firing completely. I think his unfamiliarlity with the car led to him prematurely diagnosing, relying on his instruments rather than his senses. To anyone who watches it run long enough, its obvious its not right.

 

Damn I bet your ready to push it over a cliff and call your INS. company!!! Man, intermittent problems are the hardest to track down. It sounds to me you have covered all areas and exhausted any possibilities. Just beat on it till something breaks, at this point it seems like pissing in the wind. Good luck bro keep us informed either way. ~~~rob

 

Chris-Could you explain what the miss feels like? I have had a miss for over a year and a half now, and it feels like I am hitting a rev limiter at 5k or so. It started with misfire codes and then at WOT in 4th gear one day the opti self-destructed and my catalytic converters exploded (it was quite a site to say the least!). Put in a new opti and the miss was there, not as bad, but still there. So I literally replaced every ignition part. No luck, still the same. Then my alternator died and I put in a a 200amp one since I was running a huge stereo (changed to a yellow top also). Things were back to normal and the miss was there. It was a long way to get there, but here is my question.......do you still have the ABS inop light? That also appeared in my situation. The car would all of a sudden just be dead. I had the altenrator rebuilt again and he juiced it up a little bit but the ABS still didn't work and the car kept getting drained of juice. So I checked the fuses and pulled the ABS relay. It solved the charging problem but still has a miss. I'm thinking I have a bad ground somewhere or maybe a wire that has been damaged and is causing all these problems, and may be tied into the misfire somehow. I have pretty muh given up hope.......I am hoping that when I install my new cam, valvetrain, fuel pump, etc. in the spring that it goes away. Who knows, maybe it is a lifter, or maybe it is a spring issue. I have no idea at this point. I totally empathize with what you are going through. I wish I had the time and money to just tear the damn thing apart and/or go over the whole car with a fine toothed comb to look for the problem........
Brian
Edit: If you have a moment, do a search for my name in this section, I have a thread with 200+ replies on my saga that may help you out.

 

Guys Guys Guys Not everything has been covered yet....


Let me explain. Today I was looking for a possible leak in my stock manifolds and Arrrghhh!!! Those Dam things come with huge check valves conected to the Airpump!!

What if!!!! just What if!!! those check valves are leaky?


What if!!! The Airpump connects to both Exhaust manifolds with a Y type hose or T connector?? Instantaneous exhaust leak flowing between manifolds if just one of the Check Valves Fails or even if just leaking. those are one way valves but if one leaks it will flow into the other exhaust manifold and all that extra exhaust it sure is gunna make the PCM the car is running rich dont you think? (low oxygen) or what if it just blows-by right into the other combustion chambers when the exhaust is begining to close ?? sending the intake mix back into the intake manifold?? I mean Am I the master of paranoia or what????


Now I am gunna study the Smog Airpump and how it is connected to the manifolds.....


I know I know some of you guys have deleted the pump and stuff or have exhaust headers But I havent..... maybe just maybe...thats my problem.



Marvin

 

Good point Marvin. If it was stuck open or as a partial, your BLMs would be off. However, if it flutters, then you may have an issue that would run pig rich... Hmmm.