Over the last 3 weeks I've done some work to my '93 vette. New
timing cover seals, steering rack, optispark, plugs, wires, coil, water
pump, and front control arms. Got everything back together and it
seemed to run like new.

Drove it 2 times for a total of about 13 miles. Got in yesterday to take
it to the alignment shop and after about a 2 mile drive it just died
going down the road. Coasted into a parking lot and tried to start it
again. Just turned over and never hit. Checked to see if spark was
getting to a couple of plugs. It wasn't. Walked back home got a spare
coil and hooked it up. Still no start.

Had it pulled home this morning and tried to start it around lunchtime.
It fired right up. Let it run just sitting in the driveway and after about
5 minutes it died again. Didn't sputter or anything, like somebody just
turned of the switch. I noticed the temp gauge and it was at 128.
Tried to pull codes on it, which I've never done before, and couldn't
get anything. From what I understand from the FSM once you ground
"A" and "B" the service engine light should flash once, pause, and then
2 more times quickly for a code 12 and then any additional codes after
that. I didn't get the car to do this. The fans did come on and the
only thing that was flashing was "INFL REST" about 4 or 5 times with
no pause. Also "service asr" and "service abs" came on briefly. After
that checked for spark at the coil. Nothing there.

I could check fuel pressure but don't really think that's the problem
since there is no spark. Does anyone have any ideas? If I could get
codes maybe I could walk through the FSM. Does the fact that I'm
not seeing any codes, not even "12", indicate the computer isn't
working right? Or maybe I'm checking wrong. I put a paper clip in the
1st 2 terminals from the right on the top row. This looked correct from
the diagram in the book.

I'm really out of ideas. I'd appreciate any help. Thanks.

 

One other thing. Just went out and tried to start it again. Started for a second then died. Started a second time for a second and died. 3rd try won't start and no spark again.

 

Do you have the Factory Service Manual or did you reference another "book"?

 

Could be a defective Opti...What brand did you install? Some of the cheap ones are not very reliable.

 

Pull codes, use a paper clip and ground pins A and G, these are the top right pin(A) and bottom left(G).

ICM and opti come to mind, ICM being tops.

 

try this to pull codes Hope it helps http://www.corvettebuyers.com/c4vettes/codes.htm

 

Optispark and coil are MSD. I do have the actual factory service manual. 2 books. I was jumping pins A and B. I'll try jumping A and G though. It did start again and ran a few more seconds. Seems like the longer it sits the longer it will run when it starts. I'll go try to pull the codes again. Thanks for the replies.

 

Try the ING Module. Behind the coil on head. Be sure to add white heat compound to the back of the new one.

 

It sounds like the Opti, I had an OEM Opti that was bad right out of the box, I am now running the MSD Opti in my 94 LT-1 . I would get the FSM manuals though before I pull the Opti, and do some more trouble Shooting .

 

As long as you have the FSM, there is a section for troubleshooting no code 12, see book two page 6E3-A-24. If you get the code 12 after grounding the correct pins but still have a no start see the Chart A-3 on page 6E3-A-26, it will guide you through a step by step procedure to isolate the problem.
The flow chart method can be cumbersome but if you follow the steps in sequence it will usually find the problem more effectively than trying parts, best of luck.
Picture of the connector below, A & B are the correct pins

 

primary ign coil should have+12 on one terminal and if you ground another one you should see spark. Find terminals turn ign on you should see +12 on both terminals, then ground one of them (you have to know which one) and check for spark. If you hook up test light to grounding terminal it should blink when you starting engine.
There are several pretty simple ignition tests, get a book.

 

I'm having a very similar problem on my 93. It almost seems like it floods and stalls after about 5 minutes. After I let it sit it starts right up again and creates a lot of exhaust like it's burning off excess fuel. Only code is low coolant which is a faulty sensor since it's been on for a year or more now and has plenty of coolant. I only just started troubleshooting, so I'll be interested in hearing if you come up with anything.

 

I did get the codes by grounding "A" and "G". They were "C12" which is normal H15-coolant temp sensor circuit, H42-Ignition control circuit, and H62-oil temp circuit. I see now in the FSM where the tree to follow each code is. I'll try the steps to determine what caused the H42. My voltmeter is fried at the moment so I'll have to pick one up tonight. Thanks again for all the replies. I'll post what I find.

 

I went through the steps in the FSM for diagnosing
code H42. Following the tree diagram it looks like it
probably is the ICM. I've ordered one and hopefully
that will fix it. I'll post back either way. Thanks again
for the help.

 

Good luck with the ICM - I still haven't found one that will last a full year.
I wish I could find the original equipment - that sucker lasted 100k miles.
Autozone - lasted about 8 months
O'riley - lasted about 10 months

I need to put another one on this week

 

I ordered one from Rockauto.com. Suppose to
be an ACdelco. It was actually cheaper than the one from the
chain stores. Should be here today or tomorrow.
If you need another might try looking there.

 

Try NAPA. I replaced my ICM and EGR solenoid switch and was able to buy genuine AC/Delco parts there in both instances. Also, be sure and apply the packet of thermal transfer grease that comes with the new ICM or it'll stir fry itself to death in short order.

 

I'll try NAPA - I've got my "emergency" ICM on there last night. Used the last of my artic silver thermal paste to put it on.
If NAPA doesn't come thru I'll order one from RockAuto, I've got to get a couple of other parts anyway.

 

I had one from napa lasted 300 mi. New MSD opti lasted 650 mi, I'm very disinchanted with these so called quality parts.The only good thing is that they had a guarentee. Tim

 

My AC Delco replacement's been on for 4 years.

ACD# D1971A
GM# 10483131