RonBrooksGA

HELP! I am at my wits end. If anyone has experienced this issue I would appreciate your advice and any suggestions are welcomed. I will lay out my one problem and then give you the story. Sorry up front for length of the post, I’m just trying to give the best info I can in the hope one of you has an idea or even experienced the same thing.

The problem is that completely at random and without warning and in seemingly any possible condition, the engine will simply cut off as if the key were turned off. The ignition light comes on at the instant the engine dies. The engine is from a 1994 Corvette.

Here is the story. Everyone has their dream car and then their dream car that is more realistic and affordable. This is mine. It’s a 1995 Porsche 968 6 speed manual with an LT1 engine swap. The engine swap kit is from Renegade Hybrids in Las Vegas. The engine harness is from Painless Performance. I have owned the car for going on 5 years. For 3 years everything was fine. Then about 2 years ago, the problem popped up. The engine will simply cut off instantly. Once it shuts off, that’s it. Now the way my ignition switch works mechanically, once you turn the key past ignition on to start the car, in order to restart the car, you have to turn the key to the off position and then you can go ahead and restart it. The engine always restarts. Renegade said they have not heard of this issue before.

The engine has cut off literally after less than 1 minute of running or after an hour of constant running. Running gently or having fun has no effect. The problem may happen 4 times in one day and then not happen again for a month! In fact, once it went just over 900 miles before it happened again! It’s died on smooth roads and once on a fairly bumpy unpaved road (I live in GA . It’s happened in 90 degree weather and 30 degree weather. Rain doesn’t make it happen any more or less frequently. I can find no constant condition to give some scenario in which the engine dies over another. It really does seem unfortunately to be completely at random.

This is my affordable dream car. I’m the 4th owner from what records I could pull together and not knowing what components were changed when, I decided that a major overhaul of the ignition system was in order so that even if the problem was not resolved, I would at least have a baseline of knowing what was changed. So, a friend of mine who is an electrical engineer x-rayed my PCM and said it was so badly deteriorated that the leads were lifting off the board and the board itself had its layers delaminating! I didn’t know who to trust to rebuild it so I called Golen Engines and Lingenfelter and they both said PCM For Less was the company. With that name I would never have selected them but I figured if both said that company it was good enough for me. So here is everything that has been done: PCM rebuilt, new ignition switch, new fuel pump, new plugs, new Taylor wires, new GM coil, new GM ignition control module, new GM vented Optispark, rebuilt alternator, new water pump, new Interstate battery.

When all was done, he started right up. Drove great for 82 miles at which time the engine cut off after running for maybe 3 minutes and having covered all of maybe ¾ of a single mile. As usual, turn key off, restart and it starts right back up. He’s been parked in the garage since. That was last week. I really don’t know what the problem could be, but something is cutting the ignition off. Just tonight I started the car and while idling, checked the wires to and from the OptiSpark, coil, ignition control module, ignition switch and the PCM pins for the ignition. I wiggled, pulled and pushed fairly hard one wire at a time in the hope of finding a loose connection. Nothing. I couldn’t find anything loose and the engine ran perfectly. I am at my wits end which is why I’m posting this at almost 1:30am.

Any ideas?

RonBrooksGA

I should also have added that the engine runs on speed density and both O2 sensors were replaced with Bosch units.

Hot Rod Roy

What are you loosing? Are you sure it's an ignition problem? You'll need to find a way to monitor several things to determine whether you're loosing ignition or fuel. Some special test wiring may be required. An easy test device is an LED in series with a 1k ohm resistor. With 12 v., the LED will shine. Your EE friend should be able to give you some good tips!

xrav22

After so many years you still have to do a tune up.

RonBrooksGA

All the work in mentioned was done at one time and the car has only done 82 miles before it died again.

Fuel pressure tests fine. I am assuming it's not a fuel issue only because when I pull the power feed from the fuel pump the car doesn't die instantly which is my issue. Is there a fuel issue that could cause the engine to instantly die?

I've been looking for a way to data log from the OBD port into a notebook computer. No luck with this so far as people report all sorts of issues with what I have found for data logging.

s carter

My car had a Stalling problem & Systems showing on and off, and a coolant temp sensor problem. I replaced the temp sensor and the Stalling problem has since stopped.

WVZR-1

If the harness is by Painless there's for sure I'd think the ALDL/DLC and a conventional "correct" scanner I'd think very valuable for maybe diagnostics. I'd maybe try to find someone close with a Tech1 or maybe a quality SnapOn MT2500. Is there a CEL/SES light used? Some Painless maybe not. I would think that Painless would use a 12 pin ALDL/DLC vs the 16 pin but I guess you check. I don't know where you've found so much information about "issues" regarding data-logging.

Maybe since the car has a GM PCM you contact a "local" and see if they'd offer up some assistance. Maybe provide a snapshot of your ALDL/DLC and mention which cavities are populated. Is the ALDL/DLC easily accessible? Is there a label on the PCM? Snapshot of the PCM/or whatever. Familiarity with the earlier PCM is maybe more difficult to find today. I think you ask questions of the shop to be sure. I would think that you should have "HISTORY DTC" stored that could help.

Through the years you've mentioned MSD - today you didn't. You've mentioned shops previously also.

RonBrooksGA

All the work I listed was done at a local shop. One that several people locally who have C4-C5 Corvettes recommended. I went with all GM parts this time because I was hoping that not only might this major service fix the problem but that if I went with all OEM it might give me a good reliable baseline to work form if the problem wasn't fixed.

The data logging issues I found related to people who sold various cable adapters and software to log data onto a notebook computer. Many people complained of not getting the software to work to log the data. They could get it to show the data live on the computer but the ability to save the data was problematic. Since my problem is so erratic, I would need to save the data while driving and see what it shows when it dies the next time. There is a CEL as part of the wiring harness. It has a 16 pin connector. I've attached an image which I hope works. Looking at it the way it's mounted you can see only the bottom corner pins 1 and 8 and the top 4, 5 and 6 pins are used (counting left to right) You are correct about the difficulty in finding a shop with someone knowledgeable about these cars. Everything seems to be geared to the LS motors. That's an engine swap offered for my car by Renegade Hybrids but not in the budget. After all the above work was done, my local shop essentially threw up their hands.

billschroeder5842

If I'm not mistaken that connection is for an OBD2...

So let me understand:
95 Porsche 968
LT1 Swap
Painless wire harness with OBD2 (that would be from a '96)
Unexplainably dies

I'd be guessing an Opti, but guess it would be..

As WVZR-1 suggests, plug in a scanner and start looking at values

WVZR-1

These cavities are populated 4-5-6-9-16 and that seems reasonable for a '94 PCM use for RUN ONLY. When the change was made to the 16 pin DLC I believe the ability of "FLASH" faults went away. A scanner is needed. I borrowed a 16 PIN adapter to use with my Tech1 when I did a friends ParkAve ('95 but with 16 pin DLC) BUT I also used my Tech2 for the same car, both worked but I did have an unusual response when comparing. I don't recall what it was.

I'd maybe try to get someone to use a Tech2 and use the '94 menu functions. If you can get history codes I'd think it would be a help. Has it ever lit the CEL? AT KEY-ON not running does the CEL light until crank, light and then go out before crank or ............... It might be itereesting to see what values are actually functional in the menu.

I asked CEL and it seems you maybe confused CEL for DLC - the image is the DLC ...is there a CEL/SES "lamp"?

The Tech2 current menu will do a '94 F,Y,B with P engine

I wouldn't think that data-logging should be an issue either but I've not used anything since Diacom long, long, long time ago.

Having posted your DLC pinning I'd think that someone that does newer "data-logging" can maybe explain some available options. If the Tech2 works or a Tech1 with a correct adapter either will do "snapshots".

RonBrooksGA

The CEL lamp is to the left of he connector. It just isn't in the photo. The light comes on as soon as the ignition is turned passed aux to ignition on. Then as soon as you engage the starter it goes out and stays out, until I get the dying issue then it comes on exactly when the engine cuts out. It is odd Painless Performance uses an OBD2 connector but that's how it comes from them. Here is the connector with the CEL to the left.
I will start looking for someone near me with a Tech2.

jmgtp

Years ago my 94 had a similar problem. It wouldn't die completely but it would cut out and the tach would drop to 0 during the cutouts which lead me straight to an ignition problem. I fussed with replacing the coil and ICM and it would run ok for a bit before acting up again. I converted to LS1 coil packs using the LTCC kit. This eliminates the HEI coil and ICM and use of the high voltage side of the Opti. It still utilizes the resolution signals from the Opti. This solved my problem - which made me believe that the high voltage side of the Opti was failing. Keeping the original Opti also keeps the high quality Mitsubishi sensor that aftermarket Optis do not have. The LTCC kit is expensive but it's made life easy and I've had zero ignition problems since.

Id be looking at ICM, coil and Opti if I was you.

I know you're running the motor in a Porsche but a 94 Corvette FSM will help you troubleshoot.

Rich Levittown

I think I just sprung out of lt1 ignition hell.
My ignition kept cutting out usually from driving mre than 20 minutes. So I figure it's a thermal intermittent.
Replace ICM and coil. Separated the ICM from the cylinder head. Still developed same intermittent. I replaced the opti last year and I think I would rather drive it into Houston before I change it again.
So...I grabbed an old Pentium heat sink. I was about to put it back to back with the stock aluminum heat sink.as i was about to bolt it together, I noticed the stock aluminum heat sink was a bit curved to mate with the CPU heat sink. Low and behold, it is also curved and didn't meet the ICM the way is should. It rocked and not in a good way. So I just went with the old windows 98 heatsink to improve upon the stock piece of garbage that was mouted to the cylinder ****** head for added cooling. And no. It won't be mounted back that way. I'll mount it permanently somewhere soon even if I have to add wiring. Fingers crossed...