Nothing yet, I have been really short on time the last few weeks to work on it.

Supposed to be about 60* here friday so I'm planning to take a day off work and mess with the car.

Every wire in the primary ignition system has been checked for continuity and those that carry voltage when running or key-on have been checked too. THere does not appear to be anything wrong with it.

I bought an antique analog osciliscope from Ebay and am going to try it to see if it picks up anything a digital scope could have missed. By antique I mean this thing is probably mid '60s era, but it works.

The plan is to do that, pending results, then I am going to break down and put yet another opti on it, and if that doesn't cure then I'll probably pull the tq converter and have it sent to PI to be sure it is in balance (the miss began--or at least was exposed--when the converter went in in '02) And if that doesn't fix it I guess I am pulling the motor.

 

Did you reinstall the TC in the same orientation as the original?

Also, when I had my PI changed to 3 cltuch unit, I started to notice things I hadn't before. Such as 1st gear PWM of 87% IIRC and other thhings that appear as misses. Are you running a std unit?

 

Yeah its a single clutch lock up unit, 2800 stall. It is installed correctly, but I immediately felt more vibration and started to get more missfire codes.

I simply assumed the lower mass converter had less of a dampening effect on cam lope, etc. and the PCM was sensing that through the crank sensor, so I never paid any attention to it. Only when the car was cutting out on the dyno did I realize I had a problem that needed fixing.

But I've been focusing on the ignition because I haven't been able to establish any rationale for how a transmission issue would case the ignition to cut out. It would also jump out of lock-up on the highway due to the missfire codes but I have missfire detention off under 2500 rpm now.

As a matter of fact, last time I drove it, when it died on me, I was on my way home from work and threw it up in 3rd to accelerate off an interstate merge, and the RPM got up to 3000 and on came the PO300 code.... so the converter unlocks on me. I pulled out my PDA based scan tool and deleted the code, then 5 minutes later on the off ramp the car starts sputtering and choking, eventually dies.

 

The reason I felt more was because the PCM will command a bit of lockup. However, because the 3 disc setup act more like an on/off switch, I felt stuff that never before was a concern.

You might try disabling the lockup at the tranny and see what the result is.

 

Well the only problem with that is it doesn't occur only at lockup, its there all the time, at idle, part throttle, WOT, cruising in lockup.

I have wondered if the balancer it self is out of balance.

 

I did make some discoveries/progress this weekend:

Jack at Precision industries says all their converters leave the facility balanced to within 5 grams, and it would take an imbalance of over 250 grams to feel at idle, and would only get worse at higher RPM. So the tq converter as a source of problems has been ruled out IMO.

Did some troubleshooting Friday, the scope showed everything looking normal on the secondary ignition. Analyzed another car for comparison and nothing seemed unusual.

However, I think I did diagnose why the car is dying. After it runs for about 10 minutes, it just cuts off. It will crank but not start, then about 30 minutes later it fires right back up. Turns out that there's no spark, not at the plugs or the coil. Ignition fuse is hot, 12.5v is seen at the coil and module, and my old coil didn't help either. I believe its the autozone optical section that's doing it. So I have a new opti coming from Jason Cromer this week and will install Saturday.

So I'm now down to this: 2 separate issues, this "miss" and the dying. The dying only began in Dec. when we put the new optical section on. So a totally new GM opti should cure that and at least get the car drivable so I can get my tags renewed and emissions tested. As for the original miss...I suppose there's an off chance yet another Opti will fix it, but I doubt it, since the scope didn't show anything wrong with the ignition. Current theory is that I could have lost compression in several cylinders but oil control rings are still in good shape, hence why its not smoking any.

I plan to drop the headers at some point to gain access to all the plug holes easily. Not been able to test more than 2 cylinders so far because its so hard to get the compression gauge fitting in there.

 

That is an interesting find. Let us know if it was the opticrap from
AZ.

Good luck!

 

Thanks for keeping this active Chris......I wish I had something to add, but I don't. I have been having issues with misfires forever, so what you find may help me and a lot of others with similar problems.
Brian

 

If I ever beat this maybe I'll write the ultimate missfire diagnosis article, LOL.

 

wow i cant believe this thread is still alive.sorry u havent found ur source yet.but u mentioned when the miss hits the lights dim,guess what thats exactly what happens in my car also.ive gotten the miss down so it only happens at idle..i got my miss cut down i think by swapping out the o2's to ac delco.my pass side harnesses were fryed so i had to cut the harnesses off and heat tape and crimp the wires together.after i did that i got an SES so im going to sodder the wires this week and makes sure their not crossed.

i havent drove my car in months now,its hibernating but before i put it away i freescanned it:my map sensor was reading low voltage so i put an ac delco one in,my pass side bank is running very lean b/c my header bolt is backed out.within the couple weeks im doing a complete suspension overhaul(hals,dms,adj pan,tie rods,ball joints),fixing the intake man leak and sodering the o2 wires.then i ll scan it and see whats goin on.if u can email me at ledfootz28@hotmail.com id really appreciate it,i think we have a similar problem

 

that alternator idea sounds like a good caulprit for the lights dimming also.my bad and starter is 100% but not sure about the alternator.

 

We had your exact same problem once in a friend's 94 T/A, and it turned out to be a grounded alternator wire.

 

Good news and bad news.

A brand new GM opti has cured the dying problem...I can now drive the car again.

Bad news is I believe the Miss has been effectively narrowed down to an engine internal issue.

I think I may have a couple of cylinders down on compression.

Drivers' side was

#1 = 210psi
#3 = 210 psi
#5 = 210 psi
#7 = 195 psi, that's an 8% variance. #7 plug is also really sooty and that cylinder does not run as hot as the others...sometimes its hotter and other times its been nearly room temperature.

Anyway, have not had a chance to check the pass side cylinders.

 

Sounds like we're both at the same point. The shop that's doing my car is performing a compression/leakdown test tomorrow, so I should know something then.

Have you checked for a bad valvespring or collapsed lifter yet?? I'm praying that's what my problems are stemming from, I really don't want to do a new motor yet.

 

Springs and lifters are new...