Hi everyone. I reacquired a old project today and need some help.
Its a 93z car. M6 with a built LT1, forged internals, cam, full MSD ignition(6al box, opti, coil) I got the car running pretty good. it had a monster exhaust leak when I first got it which I fixed. Now when I've got it out on the highway the car will cut out randomly and when it does it the SES light comes on and off with each cutout the car makes. I can go at WOT and then slow back to speed limit (65ish my speedo isn't working right now) and thats when its the worst. after it does it's deal, the car hits a wall at 3K rpm like it's hitting a rev limiter... IAC valve? Ideas?

 

Honestly it sounds like an ignition system issue. I would see if you can retrieve the code, that may be very helpful.

however, it does sound like it could be an opti issue.

 

If the SES light comes on the ECM is storing DTC error codes. U will need an OBDI code reader or maybe in '93 (lucky for u) u can still short 2 pins on the ALDL connector (A & B) to get the SES to flash as dots and dashes to make the codes (just google for this: http://www.neilkline.com/Tech%20Tips/obdcodes.htm). The ECM stores a history of the codes unless the ECM power fuse was pulled (or batt disconnected).

Let us know what u find,
cardo

 

Do what cardo said.

If you have a laptop, you can also get scanning software and a cable from places like TTS Power Systems. I would like to get a setup like that for myself.

 

I'll try it again. Last time I owned the car I took it in to get scanned and the scanner wouldn't communicate with the computer/the port. As far as I know you can scan a obd1 car with a obd1 scanner. Am I wrong?

 

Assuming nothing has been messed with, on a 93 you could use a paper clip and jump the A&B pins as described in that link that cardo posted.

I'm no expert on OBDI and OBDII, but it may be getting difficult to find places with OBD1 readers. I know places like Advance Auto and Autozone used to scan cars for free, but I've heard of people having trouble getting OBDI codes pulled.

If you're interested in being able to perform your own scans, which is probably a great idea if you plan to keep the car, do a search on Datamaster or Scanmaster. I guess there are a lot of places that offer scanning software and cables.

 

I run into early cars all the time that won't communicate. The problem is most always a poor connection at the ALDL connector. I usually hold a rag under the connector (to protect the carpet) and spray electrical contact cleaner in it, then plug & unplug the scan tool a couple of times. My old '95 Camaro test mule need that almost every time I plugged in my Tech2.
Might try that.

 

My 93 had the same problem when I first tested my moates cable.

Quick cleaning and its been fine ever since.

 

You can get the ALDL/usb connector but you can also jump two pins in the diagnostic port. Should be in a haynes or chilton or you can check shoebox's site for details on the pin location. It won't be as detailed as a ALDL/usb connector and laptop but you'll get an idea without spending cash.

 

 

^Thanks RamAir95TA you da man.I did get lazy haha.

 

If the SES light is flashing it means misfire.

Not saying it is sounds like Opti issue, I had a MSD fail after a short time. 2nd day I had my car it failed. (Was installed before I bought it forget the miles might of been like 10K)

 

Well I went out today and messed with the msd box a bit more. Turns out it was a timing issue with the 6al. I reset it and now it's running great (for now)

 

More often than not (case in point) an aftermarket ignition adds unnecessary complexity to an already robust factory ignition system.

I would remove it altogether because it adds nothing in terms of performance or value.

 

Unless you are running Nitrous or Boost need to pull timing or 2 stepping.