I posted in another thread about my situation - thought I'd lay it all out and see if anybody has had this happen to them!

My '92 Vette has had problems for the last couple of years now; it's now to the point the engine will not start at all.

Two years ago I had the car die whenever the engine reached operating temp - street driving, highway, idling - whatever. NO CODES THROWN.

Bought a fuel pressure gauge - 42 psi - good. Went through the routine - changed Opti to a reman (bad idea) - changed coil, ICM, ECM - ultimately found the "new" Opti was bad (reman failed at elevated temps).

Having learned my lesson, I changed out to an AC-Delco - converted it to vented design and sealed the crap out of it with black RTV. And yeah, I made sure it was keyed properly when indexed to the cam - she slid into place nice as you please - no forcing issues at all.

Happy as can be, drove the remainder of 2004 and all last year with no problems. Now it has raised it's ugly head again - only this time, she didn't start again when cooled down and is now totally dead in the water. And, also again, there are NO CODES THROWN!

This time I have the FSM's - to start with, I double-check fuel pressure (42PSI - good). Then I check for continuity on every damn ignition circuit and all ground circuits in the engine bay. Then I go through Chart C-4 in Book 2-

Chart #1

no spark at plugs
no spark at coil
12v from coil fuse in fuse block to coil terminal B gray connector
12v at A and D terminals of ICM connector
AC test on B terminal of disconnected ICM plug while cranking - no reading - this is EST signal from ECM

Question - manual is kinda vague - do I measure this EST AC signal by backprobing with the ICM connector plugged in or with it disconnected as I did it?

Go to Chart #2

Check for low resolution signal via Tech 1 diagnostic - ain't got one...hmm! If I assume there IS a signal, then the EST is bad and therefore the ECM is bad. If I assume there is NO signal, I can follow the chart further downstream -

Check terminal C on Opti connector - 12.8V - good
Check terminal D on Opti connector - good ground
Check terminal A on Opti connector - 4.8V good
Check terminal B on Opti connector - 4.8V good

What this boils down to is, without the Tech 1 I can't tell if the ECM is bad (again!). Assuming there is no low resolution signal, the flow chart tells me my 2 year old AC-Delco Opti is crap (again!)

Are there any other tests that I can do to solve this riddle - did I miss something in my diagnosis so far?

My nearest dealer is over 30 miles away and I don't feel like having it towed out there; I asked but they can't test the ECM without it being in the car. Is there an alternative to this Tech 1 device, or does anyone have a spare 16159278 ECM that I could borrow?

Oh yeah, I also double checked to see that I had the vent hoses the correct way to vent the Opti - all good. Also, no water pump issues. Hell, I haven't even driven the car in the rain the last two years and am religious about not getting water in the engine bay at all!

This is gettin' real old, and you should hear the jokes my significant other is making about my pride and joy! If it is the Opti (again!) I have little or no confidence that even when I change it (again!), that this isn't gonna happen to me literally "down the road"!

I've thought about turning it over to the Goodwrench folks, but I tried that back in '03 - they "gave" me about $900 worth of service (including new injectors), but didn't cure the problem - I found the faulty Opti on my own later that summer.

Sorry to be so long winded - if anyone can shed any light at all on this, I'd surely be in their debt!

BTW - Looked at the Dynaspark - the new owners' website seems to be faulty - are they still selling them? Also looked at MSD - might go that route instead, should the Opti be the culprit (again!)

Lastly - since I'm in this deep, can the Opti be tested should I go ahead and pull it (again!)?

 

I didn't read all your post... mainly, because I got a brilliant idea as I read it!

Jet-Jock had a problem very much like this last fall. The final cause was a bad connector to the ICM.

It was hard to find, too!!

This is the thread! It has a lot of good diags burried within.

I have no idea about DynaSpark...

 

Yep sounds like the ICM to me too.

 

As far as I'm aware, Dynaspark is still in business. Suggest you call them.

Re: testing an Opti, if there's a problem in the high-voltage side, you'll usually know it because you'll have misfiring, etc. I'd think it's unlikely that a high-voltage problem in the Opti would cause a no-start, and the fact that you have no spark at the coil says forget about the high-voltage side of the Opti, as you're not even getting spark to the Opti. If the optical side of the Opti is failing, it will set codes. If I recall correctly, it's a code 16 for low-resolution sensor failure and code 36 for high-resolution failure. If you're getting no such codes, I seriously doubt there's anything wrong with your opti.

Be well,

SJW

 

Many thanks Bogus!

You know, I searched for that thread and never could find it! Will go over it in detail -

FWIW redeasy- I bought another ICM and tried it last night; no soap, no fire - no spark.

Lastly, SJW -

That's the best possible news - I know Goodwrench figures that's the answer, but I agree with you!

I was told to check the coil for proper ground - but that white lead goes through the tach filter to accomplish that. To verify the ground circuit, should I get continuity from terminal A of the gray connector to ground? If I don't, is the tach filter to blame? If I decide to bypass the tach filter, can I just run a jumper from that white wire to ground?

So many questions - just know enough to make myself dangerous!

Will try to post tonite - lousy weather - rain and 40 mph winds!

 

If you haven't already done it get some electrical contact cleaner and a toothbrush and pull the connectors and clean them as well as you can.It is cheap and and will help eliminate another possibility.

 

This is sounding more and more like the harness to and from the ICM. I will be curious what all you learn.

 

Gotcha - already been there - Radio Shack sells CAIG DeOxit - its a two part product - a cleaner and a compound that improves conductivity - they come in small spray bottles - I apply it to Q-tips (less waste) and use those to clean all contacts.

Gonna have to wait 'til tomorrow - 45 degrees, rain and wind gusts to 40 mph here right now!

Later!

 

Consider this response a question, not a recommendation. I understand, and may be wrong, that without oil pressure reading the LT1 will not start. When cranking it over is your oil pressure gauge giving a reading? Probably a dumb suggestion, but who knows.

 

aminnich - that's not right. It's a popular misconception, tho.

What is DOES do is the oil pressure feed has 2 sensors on it. One is the gauge sensor, the other is an oil pressure switch, that will fire the fuel pump, and keep it fired. However, it will only fire the pump if it sees 4 PSI. HOWEVER (again), the FP relay will fire automatically anyway!

All of that is a fail safe so that if the FP relay fails, you don't get stranded... they are in parallel...

If oil pressure drops to zero, the engine will continue to run and will eat itself. There is nothing there to stop it.... sad, really.

 

Bogus--thanks.

 

LT14FUN, a friend of mine had the same problem with his 94 Z28. I t ended up being the opti. After the second one in 1 1/2 years we decided to put a Deltec coil pack ignition in. No more problems, and it's been three years now. The Deltec is a bit pricey ( I think around 600.00) But well worth it. I hope this helps.

 

Wow, it's like nightmare on Elm street again.

Summary of what I experienced was started chasing an engine miss. Preventative maintanence I swapped the coil. Suddenly it won't start, put the old one back in starts but has a miss. Got another new coil and ignition coil module. Put them in (oh btw you must use the heat sink compound from Radio Shack or similar to coat the back side of the Ign Coil Mod. Otherwise it melts. (grin) So it won't start with all new components. Now I knew the opti wasn't that old and I had recent plugs and wires. Throttle body was cleaned you name it. I ran the diagnostics per the FSM and got interesting but correct readings. Finally gave Andy a call, we discussed this for quite a while and over numerous calls, and after every test things tested out fine. At his suggestion I plugged the old ICM with the new coil, bingo fires right up. But the miss is there and within driving it ten miles it died on me.
Was on my way to pickup the tool to disconnect fuel lines for a fuel filter replacement.

She was at ops temp when it died so while I waited a few more minutes it fired back up and I drove about 2 blocks and it died again. I was getting codes and there were indicating a short in the ICM and loss of serial I/O to the ECM - CCM. While waiting and sweating on the hottest record breaking day in the summer in central Florida with a transparent roof vette I waited with the hood up until it would cool down 30 degrees. Then I could start and run for about 6 blocks and repeat. Nearly 5 hrs later I get back home.

No for the fun part, so we run the test again lots of PM's. And finally another member (I'll think of his name) jumped in and isolated the problem with the new coil and ICM not working together. Apparently my tach filter was going. So I had to rent a car and run over beachside to Ecklers to get a Tach Filter. And stopped at BIll Heard to get an new ICM harness (remember my codes short). Got back spliced in the new ICM harness (gray side of coil connector) and splice in new tach filter. Reinstalled new coil and ICM (other one melted) this time I got a new tube of heat sink grease. She fired right up.

Yippee right, NOT. As soon as it got to ops temp (and I was clever on this one, I just drove around and around my subdivision block passing my house waiting to see if it would die when it got to temp) and guess what damn straight started bucking and I was able to make it into my driveway and garage. Whew. Ok so now what.

Well cleared codes during that process to see if new ones were set and yes I got Serial I/O DTCs again. So that means I have to freakin pull the CCM out and disconnect the ECM and test continuity between the specificed primary and secondary serial data link lines. Guess what, it was good continuity. So I pulled that out for nothing (well not exactly nothing), but it took about 4 hrs to get it out. So while it was out I tested the data lines between the EBTCM as well. Good now back together I have now isolated the ECM. Order a new one, when I go to swap the EEPROM you can smell burnt silicone my ECM was nearly fried. Anyway pop in the EEPROM connect fire away test every thing is good again.

Lots of time, money for parts, money for a rental car and hours of frustration, (and patience from Andy and help from our other friends as well).

Oh btw, the miss was still there I found out a year later when I replaced the intake manifold gasket that the aft two cylinders on each side had instake gasket leaks which were causing the miss. Solved horrible oil leak and upon startup fixed my miss too!

So I hated her when she was sick but still luv her now.

Anyway maybe my experience will help you soom.

Have you tried swapping out the ECM?

I'm in the middle of laying wood floors but I'll try to run your process in the beginning using my FSM to see if what your getting is telling you something.

It is possible the tach filter could be weak.

But the description of dieing when it gets hot leads me directly to a heat soaked ECM causing either solder connections to fail or even IC's to fail. And if no serial data is sent it shuts down.

I'll check back I have to get busy here...

 

Lani,

If the serial data line was shutting down, wouldn't there be a CCM code?

 

Anytime!

 

Many thanks for the post Jet-Jock!

I've cut up your post and inserted bold text where I've got questions if you don't mind!!

I'm going to review this and your previous thread in detail so I can make a plan for tomorrow! Please pardon my ignorance on some of these issues - I don't mind being schooled here on CorvetteForum in order to become a service tech!

Many thanks all!

 

Check the connector that sits in the passenger side of the intake manifold, this carries all of the signals from the Opti, Ciol and ICM to the ECM.
The fact that it happens when the engine is hot leads me to believe there is a bad connection somewhere.
The ground for the ICM and Coil is located on the front of the cylinder head near the coil. Take this off and clean it as well.

 

Yes I believe I mentioned it as a Serial I/O DTC but I believe it was H72 on the CCM module.

 

CCM = Central Control Module.

Climate control is known as the C68 Controller or HVAC controller.

Not sure if the page numbers will be the same but look at VIN P engine Runability section (first part of book 2) and look up Ignition Control circuit. DTC 41 page 6E3-A-73.

Sorry about that, EBTCM = Electronic Brake Control Module (ASR) Your year may not have that, not sure.

Right but you that doesn't tell you if you have an IC (integrated circuit) chip with a gate failing when it gets hot. Continuity is check to ensure valid primary and secondary data lines are known good.

Same here mine replacement the cover looked like them spray painted it black in the desert. All kinds of crap in the paint they don't seem to bother to clean up the covers.

Yes when I tested mine old tach filter after it was out of the vehicle it was really low on resistance.

Could be, I wouldn't be surprised if the reman'd ECM is failing again.

Matter of fact I'm looking at my ECM again too, as I'm getting symptoms that are beginning to mimic what I experienced before. So I'll be giving Chris a call to discuss warranty issues.

 

Hey there!

Yeah, I checked that connector after I cleaned and reconditioned it with my CAIG DeOxit stuff. I pulled the connectors from the ECM, the ICM and the Opti and traced the wires via the FSM (acronym heaven, ain't it?) I have continuity on all of them.

I know this doesn't eliminate it for a heat-soak no-start, the fact that I've been dead in the water for the last couple weeks kinda renders that a moot point. If I get it running and she dies out like she used to at temp, I'll check that connector again!

Thanks!