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yakster333 06-20-2014 05:31 PM

1994 Z-28 keeps dying
I'm not sure whats going on but the Z recently just started dying on my wife while driving.
I took a look and saw the battery was busted, I assume from the sub zero winter we had, and acid had been leaking and some corrosion.
Cleaned it up, put new battery in it yesterday, cranked it, ran fine, no codes/lights coming on.We drove it a mile back up the road and back ran fine.
Today she went to goto work, got about a block from the apt. and it died, I went and got in it, it fired up, I got halfway back to apt. and it died, would not restart, let it sit a few min. it would crank, run then die. did this a few times, then I cranked it once and drove it home.
All that said, this is what I have done since 08 to it.
In 08 this forum helped me bypass the Vats on it as it would not crank, we solved that back then and been working fine.
Last year I put new opti, wires and plugs in it. As well as waterpump and hoses.
Also in the last year the key just started being weird and tricky and you can now pull it out.
I am at a loss as I am no mechanic and we cannot afford one as I am disabled.
I would greatly appreciate any help or idea's as to what or which direction I should be looking at.


Injuneer 06-20-2014 06:08 PM

Re: 1994 Z-28 keeps dying
How did you determine no codes? There are fatal codes for the Opti and ICM that will shut down the engine, but do not turn on the SES light.

Additionally we are starting to see a lot of problems with the 20 year old ignition switch. Melted contacts, etc. causing intermittent problems.

yakster333 06-20-2014 06:39 PM

Re: 1994 Z-28 keeps dying
Sorry, I assumed the SES light would come on for them all, I will have to hook it up to the laptop and see if it has any codes being thrown. Will take me a few days to get my stuff together..
Also, I believe its either the ignition or the bypassed vats, but I don't know, what doesn't make sense to me is how it can sit a bit then start, like something reset.
When it dies its like I pulled out the old killswitch chip, it just dies. (That chip was removed when I bypassed the vats.)
Is the ignition switch hard to do? I can do anything on it with the proper help and instructions.

Thanks for the help.


Injuneer 06-21-2014 12:05 PM

Re: 1994 Z-28 keeps dying
Intermittent problems can be due to heat soak of things like the ICM and the optical module in the Opti.

Shoebox has a guide to troubleshooting and replacing the ignition switch:

4th Gen F-body Ignition Switch Replacement

SA68SS 06-24-2014 12:06 PM

Re: 1994 Z-28 keeps dying
I would suggest you try a new coil. I recently had this similar issue with my 93 LT1. The car would start 'bogging' and the tacho needle would surge, then the engine would cut out. It would recover and run well after a cool down of 30-60 minutes.

I suspected the ICM but could not get one, so I changed out the coil and so far, so good...easy and cheap fix. Around 30 dollars at any auto store.

I also have a new two-pack of Heat Sink Compound from Radio Shack (part # 2760255) and will apply it to the back of the ICM. I am just waiting until I am sure the ICM is still good.

I noted the PO put a couple of castellated nuts between the ICM and the head, probably to reduce heat soak. Might be a good idea, might be useless, but it is also an easy task and should reduce heat to the ICM.

Good luck

yakster333 06-24-2014 02:47 PM

Re: 1994 Z-28 keeps dying
Thanks for all the help guys, I truly appreciate it.
I haven't got around to checking it out yet, but will in the next few days hopefully.
I think I will start by checking out those resistor solder points I bypassed the vats with in 08, as that would be the easiest culprit I feel to start with.
Then I will hook it up to a laptop/rental and run a diagnostic on it, then work down the list you guys have given me from easiest/cheapest, to the hardest.

I just pray to god I can figure it out soon, or rather able to get out there and figure it out. My wife's been getting rides back and forth to work and its getting old.

I am also gonna yank the new battery out and look at all the surrounding wires again as I remember some of those small wire cover/protectors had been eaten thru by the battery acid that had leaked, but the wires all looked good, but I will check it all out again.

Thanks again for all the input.


P.S.- SA68SS, I am assuming you are talking about something similar to thermal paste I use with working on P.C.'s? I will check it out. TY.

Injuneer 06-24-2014 05:05 PM

Re: 1994 Z-28 keeps dying
Spacing the ICM off the head is a popular modification, and seems to help:

4th Gen LT1 F-body Tech Articles

SA68SS 06-26-2014 09:48 PM

Re: 1994 Z-28 keeps dying

Originally Posted by yakster333 (Post 6964861)
P.S.- SA68SS, I am assuming you are talking about something similar to thermal paste I use with working on P.C.'s? I will check it out. TY.

Yes. GM sells a heat compound grease, and so does any good hardware store or auto parts store. But consensus on a few forums agrees the GM ICM is the best, and the Radio Shack Heat Compound is the best.

It is a 6 dollar investment. But if you got free stuff from work...well...

I also like the look of the Airtex ICM. They are pretty proud of their product and I will be getting one as a spare.

Best of luck - I hope you find an easy fix.

yakster333 07-12-2014 05:49 PM

Re: 1994 Z-28 keeps dying
got a laptop, could someone so kindly recommend a good free obd1 software program? I am anxious to get this hooked up and hopefully figured out.

Thanks all...

Injuneer 07-12-2014 06:24 PM

Re: 1994 Z-28 keeps dying
Look at the "stickies" at the top of the "Computer Diagnostics and Programming" forum for a link to a free download of Scan9495, specifically for your 94.

It's also covered in the "stickies" at the top of the LT1 forum.

yakster333 07-29-2014 10:19 AM

Re: 1994 Z-28 keeps dying
Well, I finally got a rental laptop and run Diagnostics on it, looks like I need a new opti as the only code I get is that high/low resolution one.
Its a bummer as I just put that opti in it almost a year and a half ago, guess I didn't get a good enough one, I am disabled and no income my wife keeps us barely making it and we got what we could afford, just suck's as it took me so long and so much struggle to do it myself, good news is I can change an opti now much faster, just gonna have to save or find one cheap that's worthy.
I was warned with the last one, just got what we could afford.:(
I would almost think of selling it as it is, but that would be hard to do with it just running for short periods of time.

Thanks for all the help my fellow Z friends.


HardcoreRM125 08-01-2014 04:37 PM

Re: 1994 Z-28 keeps dying
Yakster333 - I got mine off of feeBay. Forget the user name who sells quality Opti's but it is like Miss something or MRS something. Sure someone here or LT1 Tech will remember the sellers name.


Injuneer 08-01-2014 04:43 PM

Re: 1994 Z-28 keeps dying
You may be thinking of "theoptilady" or something like that. If so, she went out of business at least 5 or 6 years ago, leaving some people with nothing to show for their payments.

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