LT1 dying unexpectedly.

Car running and then after about a ten minute drive it will die and wont start back up for about 5-10 minutes. Im still in the test phase of my project. I dont have a MAF yet so maybe that is it. Other than that all components are brand new. My OBD1 scanner wont link to my car so i cant read any fault codes. Has anybody had this issue? Any help would be great its summer and i want to drive!

Get your odb port working first and start from there.

Yep, I think they call it an OPTI SPARK!!!!!!

If it is the optispark i may flip its a brand-new gm opti

Admin wrote:Yep, I think they call it an OPTI SPARK!!!!!!

+1

If it is spark related the ICM can cause problems like that.....

Anyway to test the ICM? IT seems to happen when the engine gets to operating temp.

I believe that was a auto zone special (ICM) and if so i have learned my lesson.

Can a ICM be bypassed with a MSD box? if so i have one laying around if may be fate.

kelleysj wrote:Can a ICM be bypassed with a MSD box? if so i have one laying around if may be fate.

No, msd box still needs a signal to fire, which comes from the ICM.
Also, It is common for LT owners to space the ICM away from the cylinder head; due to the heat.
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I will try spacing it to see if that helps. Also what should I look at first to diagnose my obd1 that will not link up with my reader.

kelleysj wrote:I will try spacing it to see if that helps. Also what should I look at first to diagnose my obd1 that will not link up with my reader.

Spacing won't help if it is already bad.
To test for the bad component you will first need to duplicate the problem.
Have you determined it is indeed a spark problem?

off all the recounts of others on the LT1 forums it sounds exactly the same. Im not sure if i could duplicate the issue unless i do it after it stalls during driving which at that moment im usually on a road somewhere. I have let it run at idle but no issues then. I will have it tested if its still good re apply some thermal compound to the heat sink and space it from the head and have someone follow me on my next test run.

kelleysj wrote:I will try spacing it to see if that helps. Also what should I look at first to diagnose my obd1 that will not link up with my reader.

Check the wiring. [You must be registered and logged in to see this link.] Is yours the 12pin or 16pin?

Mine is the 16 pin. Its the 95 so obd1 with the obd2 connector.

If it is an Autozone electrical part, that is more than likely your problem.
Do not buy any electrical parts from autozone , they are mostly junk......

Not sure if it is but I'm thinking that's where I got it I will get a better look at it today.

Unfortunately when I had this problem it was the optispark...however the ICM can cause the same problem and may be the culprit...check [You must be registered and logged in to see this link.] for wiring diagrams and pinouts, that site should have what you need to check the wiring for the diagnostics port on your engine

Although...when i did have my optispark going bad, i was able to let the car sit and idle until it shut off, then diagnose, i had to let the car sit and idle for a LONG time though

^ Same here. As well, when my opti died, the computer did not put out any code...which made it all that much more fun.

Mine actually put out the code for a faulty ICM, which made it VERY interesting...you have to watch out with OBDII, i don't know much about OBDI, but with II i found out through researching that the codes for a bad ICM are often thrown when the optical pickup in the optispark is going bad...good luck brother, I'm praying for you.

Just a quick question for the original poster: When you installed the optispark, was it sitting flush to the timing cover, and did it drop on smoothly without hesitation? I ruined an opti (thank God it was used) by putting it on just a little bit off, and then trying to pull it in with the bolts...I'll never do anything that dumb again lol.

The opti was put on correctly, Im wondering why nobody has just moved the ICM to a cooler area of the car. I have plenty of wire clearance if this is a possibility i may do it. I would assume i would have to ground the ICM itself.

I believe that is a trick that I've seen used by guys running these engines in their original cars, particularly on F-body's (because I used to frequent some f-body forums)

I used the Delteq module.  Bought the coil pack on ebay for cheap.  Been running for many years now without a problem:  http://www.delteq.com/

If you use it, you can gut and seal your opti since the only thing used in it, after the delteq is installed,  is the optical sensor & wheel.  


Also, I had my '83 944 LT1 (1994) mysteriously cutting out on me to find that my oil pressure wire running to the computer was loose, and the computer was shutting the car off because it wasn't detecting oil pressure.  Little things like that are so much fun to have happen.