1995 Convertible Z28 freshly M6 swapped

I’ve had this car for about 5 months and have never gotten to drive it for more than a week and a half. When I originally bought it, it had a mild misfire at around 2000 - 2500 rpm but would drive without any other issues. A week and a half after driving it, it kept shutting off in traffic and then i could start it back up but eventually died and would not start and I got it towed home, ever since then it’s just been replacing parts and getting no change. I’ve replaced the O2 sensors, fuel filter, ICM, Coil, regapped all spark plugs, replaced all rough looking spark plug wires, Replaced injector 3, Put in M6 PCM, replaced optispark and water pump.

Before replacing the Optispark it would start every once in a while if I connected 2 negative grounds but then after that initial start and dieing, it wouldn’t start again. After replacing the optispark it started right up and I had a glimmer of hope, but it died after a few minutes, I started it again and it stayed alive a little longer with a rough idle and then died, third time it stayed alive through the roughness and smoothed out to a nice idle. After like 10 minutes of it being like that I reversed out of my driveway, put it in 1st and drove down the street and it immediately died, Wouldn’t roll start or jump start. So my dad helped tow it back to my house and now we’re back to square one.

I took it to my shop in town but they’re morons and told me it was a bad coil when it was brand new. I would like to fix it myself but I’m starting to have some doubts and think maybe I should just take it to some techs who know their way around 90s GM cars but idk.

 

At any point have you done diagnostic work like scanning the PCM, pulling codes and checking the fuel pressure?

What brand was the replacement Opti?

What was the location of the “2 negative grounds” you were connecting together?

Did it run this bad BEFORE the trans swap? Did you revise the wiring harness for the A4 —-> M6 swap? Did the clutch pedal assembly include the “clutch start switch”? Any particular reason you didn’t have your original PCM flashed with an M6 program? Was this the PCM from the “383 stroker” you got the T56 from?

Did you verify the new “M6 PCM” was the correct version for a 1994/1995 and had a stock program? Is you engine totally stock or modified?

 

I haven’t checked for codes yet because I don’t have a scanner, It didn’t have an SES light with the A4 pcm but it does now the M6 PCM.

The fuel pressure reads right around 45.

The two negative grounds were on the alternator and one of the bolts that stick out where the struts go

The opti was a Cardone from rock auto.

It ran the exact same before the manual swap, I did the swap because I thought there was a chance it had a bad pcm and thought it would be easier to just do the swap since I had the pcm I was going to put in from my parts car instead of reflashing the A4 pcm just to take it out for the swap.

I did all the wiring exactly from the Afrash write up except for the reverse lockout. Yes it was the PCM from the “383”

The only thing I have that isn’t stock is Pacesetter headers, It has no catalytic converters, I have flowmaster exhaust but the mid pipe is taken off because it was done terribly and a piece broke off inside and made it to where I couldn’t get it on without the driveshaft hitting it so I temporarily have the mid pipe off.

The problems it is having existed before the swap and before the removal of the mid pipe.

 

I have no idea what “the Afrash writeup” is. What did you do about the “skip shift” solenoid circuit? That will set a code if not hooked up, or bypassed with a resistor. Did the writeup address the skip shift indicator light in the instrument panel? That circuit can also set a code. Also the reverse lockout solenoid. Given the magnitude of your problems, the mismatch with the tune, questionable wiring, etc. you really need to get a scanner and pull the codes, if any. Without that you appear to be playing a losing/expensive game of “parts replacement roulette”.

The fact you are running a stock engine with a tune for an unknown 383 stroker is definitely complicating your issues. What if that engine had high end heads and cam? Just the displacement being wrong in the tune can be an issue. What if the 383 had huge injectors? Won't get manageable results with the stock injectors on that tune.

The Cardone Opti is not necessarily reliable. The only units that seem to be certain to run right out of the box are sold by Petris Enterprises.

The alternator does not have a ground wire. And is “one of the bolts that stick out where the struts go” the stud mounted on the inner fender near the red plastic “+” distribution box?

http://shbox.com/1/starter_charging_95.jpg

The alternator case grounds to the bracket.

When does the fuel pressure read “right around 45”? It idle with the vacuum compensation line correctly attached to the fuel pressure regulator, a stock setup will typically read 35-38 PSI. Should vary within this range at part throttle. Take the vacuum line off and pressure should then be in the range of 42-47 PSI. You would also see the 40+ readings at WOT. But not while driving at part throttle.

 

This is the write up I was talking about
4L60E to T56 conversion instructions for 1994-1997 LT-1

I don’t really know what the deal is with the two negative grounds because it was my friend who did it and he knows more than I do. All he did was hook up a black jumper cable to the alternator, and the other black jumper cable to the spot where a strut tower brace would bolt onto, but he said we just got lucky with that because after it died a few times, having those there did nothing.

I’m sorry I forgot to say I didn’t wire up the skip shift because I didn’t want it and the skip shift eliminator seemed unnecessary because I thought that the 95s didn’t throw a code for it so that is my mistake.

When I checked the fuel pressure it was with the tool hooked up to the shraeder valve with the fuel pump priming and the car off, I haven’t checked it with the car running because I haven’t had it running long enough to think of that.

The guy that I got the parts car from said it was allegedly a 383 but he wasn’t sure, He seemed so unsure I figured it was just bull**** but I know there is a chance that he was being truthful and then you’re right about that definitely wouldn’t help my case, but it acted the exact same as it did with the other PCM in terms of not starting, I feel like it would’ve acted different in some way if the 383 tune was drastically different.

I know I’m making this very difficult with all the random complications but I’m trying my best to get the facts straight.

 

You’ll likely never figure out what’s going on without some diagnostics. If you have a laptop, you can get a cable and install Scan94/95. There are people here that can help with interpreting the info. There is a big thread about Scan9495.

 

UPDATE: I took it to a shop and they just said it was some bad wires going from the opti to ICM or something like that. Car starts up fine now and doesn’t have an SES light anymore.

 

Funny thing is - there are diagnostic codes for issues with the ICM wiring. Scan might have picked up this problem known a long time ago. Could have spent the cost of the shop on a scanner, and had it available for future issues.

 

Dont worry, I already ordered a cable to hook up to my laptop. Do you or Gary still look at people’s files from Scan9495?

 

Gary just built the software. And I appear to be the only person on this site that reviews the files. And I have cut way back because it's a lot of work, and most people asking for help aren’t in it for the long run. They seem to want an immediate, single sentence with the absolutely correct statement of what part needs to be replaced. Unfortunately it doesn’t work that way. I have to ask questions about details of their engine mods, have to ask them to do some simple testing like checking the fuel pressure, or looking for vacuum leaks. They don’t want to follow my steps for making the data log. They lose interest and disappear.

At this point if I sense that someone is committed to hang in for however long it takes, willing to do what I ask, then I might take a look and respond off the record, using email or private messages on this site. But not in an open thread. I also have to make it clear that there is no guarantee that I will find the problem.

At this point, people start or continue a thread, attach the data log, and ask for help. I wish there were other people who could pitch in, but there’s hardly anybody left on this site. If someone posts a thread, I'll evaluate my chances of establishing a working relationship, and take it from there.

The preferred procedure for running a data log is in post #2 in this thread:

https://www.camaroz28.com/forums/com...-guide-886891/

The “Scanning Guide” linked in post #1 can be helpful in understanding how the PCM works.

 

Yeah that’s not fair at all for you to have to be the only one putting in all that work for strangers for free. I will definitely use all the resources that are already available here and see what I can find.

 

Normally I do not look because I am just a computer geek and know not much about your engine. If you post a log file I can give it a first look, then pass it on to Fred, if he is not busy.

 

Did you read post #7?

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