I have a 1992 LT1. Car had intermittant times when it ran terrible and digital spedo area would blank out and car ran around 175 degrees as previous owner had grounded both fan relays so that both fans came on as soon as the key was turned on. Monday I pulled the codes before installing a new battery by jumping the A to G terminals, codes were as follows CCM 1.1 H72 and H74, ECM 4.1 H16, H 28 and H44 EBCM H 62. Tuesday I reconnected the fan relays to the stock wires as I thought that the low temp may have contributed to the intermittant bad running as the computer was not going into close loop, I drove car to check fan operation, engine temp 228 and fans worked correctly, car ran fine. Wednesday car ran fine. Thursday started to miss when warm around 225 degrees, ). Friday started fine in morning, started to run bad when cold got better then again when warm, stpooed and shut car off, would not start back, ECM was very hot so I placed a wet paper towel on metal body of ECM only to cool it down, car started and ran fine, next stop I shut it off and it would not start back up, I left it for 2 hours and car started and ran fine , I got home (2 mile drive) and shut car off and it would not start back up, ECM was again very hot (engine only up to 206 degrees during drive), I cooled down ECM with wet towel again and car started. I then pulled codes, (paper clip A to G on ALDL) got the following CCM 1.1, code C12,(OK) ECM 4.1 code --- (no codes) , EBCS 9.1, code H62 (tachometer data error). I then made the mistake of starting engine with paper clip still in ALDL twice and engine statrted fine ( did not test drive) Saturday engine would crank on the starter but would not fire at all (mamy mamy tries) checked for fire at plugs and coil, NO FIRE, checked leads to coil, term A in gray plug on had 11.8 volts, neither terminal in black plug on has any voltage and car would not start. Sunday spent all day pulling all 9 of the body and engine grounds and cleaning them up and putting them back with dielectric grease ( all except the one by the passenger seat sholder harness ) car won,t start and spedo is blanked out so had to check for codes by julping A to B on ALDL and check engine light, got code 12 and 41. Before I throw money at it, does this sould like I fried an ailing ECM by starting car with jumper between A and G? I am so frustrated I just want to throw a match in the car and let the whole problem disappear.
Thanks for your help. Sorry this post is so long
Jerris

 

I would start with the basics.
Check fuel presure,Spark,all grounds,wiring under the dash where your feet are.

 

I have done all the grounds under the dash. Car has fuel and cranks fine but no spark. Tested at coil, have 12 volts at the gray connector but no volts at the black connector and no fire from the coil or at plugs. Thanks

 

Code 41 is either-prom or ECM failure, I'd check the connections to it
first, might be when you were putting rags on it you loosened a connection. But you may have also spiked it when starting the engine
with the paper clip still in.

 

Is the 92 an L98 or the Opti Spark. I think it is the Opti Spark, with which I have very little experience.

Whatever ignition system it has, you need to see if you have a primary signal at the coil. You should be able to use a test light on the minus side of the coil and with someone cranking the engine see if you get a switching light on your test light.

With an HEI as on the L98, use an AC voltmeter looking for at least .5 VAC from the pickup coil. If you have it then the coil is at fault, if not it is the pickup coil.

On an opti spark you will be doing a similar thing in that you will be looking for a switching signal from the crank trigger. I have worked with a number of different distributorless ignitions, but not the V8 Opti Spark specifically. The idea is to find out if you are getting a switching signal to the minus side of the coil. Since you know that you have 12V on the positive side and that you are not getting spark, if you DO have a switching signal to the coil, the problem will be the coil. If NOT you need to look toward the crank trigger and even the cam trigger if the Opti Spark uses one. It may not, sense it is pre OBDII, but I don't know that for sure.

You REALLY need a book and preferably a wiring diagram.

You have isolated the problem down to the ignition, so you are almost there. Get some more info on the crank trigger/cam trigger systems for your specific engine.

Sorry I can't help any further. I also strongly advise that you do not just start throwing new parts at it. Get some documentation or pay someone to troubleshoot it properly. Once you start throwing parts at such a problem, you will most likely be unlucky and get more money in the problem than if you were to pay someone to troubleshoot it.

Best of luck,

 

Make sure all ground wires are connected below the ECM. Also make certain the connectors to the ECM are fully seated. If you are not getting a tach signal things point to ignition.

 

Engine is an LT1 with a 4 month old new Optispark
Dash readout came back on and I was able to pull the codes again so dash blanking is not connected to my problem.New codes are CCM 1.1 - H25 (courtesy lamp circuit open - I had pulled the fuse to save the battery) ECM 4.1 - H41 (EST knock sensor error) These are both stored since the time car cranks but wont not start. Can a knock sensor keep the ciol from fireing???.
If the ECM was bad would I still get ECM and CCm codes????
I checked the connection to the ECM and is good.
Thanks for the help, Im lost.
Jerris

 

Have you had your ICM tested? This is responsable for triggering the coil at a precise time determined by your ECM.

Although more robust, and less likely to fail, have you checked to see if your coil is bad?

Did you check your cap and rotor ? Edit: whoops, i just saw that you have a fairly new Opti.....But check to make sure your coil connection to your Opti is solid!


These are the first 3 things I would verify if you are not getting spark.

 

Is it just me or does 11.8V sound a little low?How is your battery?Put a charger on it.That hot ECM troubles me I would not use to much water on it.You can take the plate off the bottom of the ECM and reseat your prom.It is just like computer memory.While it is open take a sniff I assume you know what cooked electronics smell like.

 

You need to get a manual and trouble shoot this code

 

I'd lean HEAVILY toward an ECM. I had intermitent and seemingly unrelated problems with my '92 that I chased for a week before finally believing the service manual and replacing the ECM. Presto, car ran better than new!

Starting with the 92, the ECM controlls EVERYTHING! Spark, fuel, fans, you name it. Oddly, they don't seem to simply stop working but rather get very flakey and have you chasing your tail.

See if there is someone in your area that has a '92 (one year ECM) and try swapping it. In the mean time, put a charger on your battery, I'm sure it's getting weak from all of the attempts you've made already.

 

Had heat problems with my 93 but with different symptoms. The serial com link would fail and then work after I put a bag of ice on the ECM. The ECM gets cooked under the hood and average time multiple heat soaks cause electronics to fail (PC board lands fail, solder joint failures, internal chip failures, cap failures, and on and on).

 

Put a new Coil and module ( the one that mounts on the coil mount) in today. Car still would not start. Checked for current at injector wires, current on green wire, no current on brown wire, no start. Checked for codes as dash LED was working again. Codes as follows: CCM 1.1 - H72 (LCD dimmer open), ECM 4.1 H36 (Optispark high resolution timimg) and H41 (EST knock sensor), EBCS 9.1 - --. CLEAED CODES
Went to check current across injector and CAR STARTED DURING TEST(voltage across injector was 0.4 VAC and while running had current at both injector wires and test light blinked). Let engine idle to bring up to temperature, engine shut off at 186 degrees and would not start back although it did have intermittant fire and acted like it wanted to start sometimes. Checked codes as follows: CCM 1.1 - C12 (OK), ECM 4.1 - H41 (EST knock sensor error), EBCS 9.1 - H62 (Tachometer data error).CLEARED CODES
Now Im back to square one, car cranks, no spark to plug wires and as often as I crank it and check and clear the codes I get the following coded ECM 1.1 - C12 ( ok), ECM 4.1 - H41 (EST knock sensor error) , EBCS 9.1 --- (No code)
I think I will replace the knock sensor tomorrow night but Im starting to feel like Im throwing parts at the problem.
Has anyone had any experience with the knock sensor causeing the ECM to not trigger the spark? Or does this sound like the ECM is the problem? Or is it the Opti? (Opti is only 4 months old and tomight the car ran fine without any misses while it was started)
Plesea HELP anyone.
Thanks
Jerris

 

I just went through the optispark drama about 4 months ago. I had to replace the opstispark plugs and wires. I also replaced that ignition control module that sits above the coil 3 times because I kept shorting it out. Possibly because I left the paperclip I was using to check codes in the interface and tried to start the car. If you did that your ICM is most likely fried. I wasn't reading my Chiltons manual carefully enough at the time. I learned quick to do so. That small part will definitely give you a no start condition. Sometimes it is intermittent like you are describing. I couldn't believe it but that was the problem on my car. Take your ignition control module to Oreilly's auto parts. They have a tester for the ICM that takes 3 minutes. Take your coil to Autozone. They have a tester for that. Double check these even though you just bought them. You are having the exact same problem I was having.

Remember to put that packet of white silicone grease on the metal plate your ignition control module sits on. If you don't it will fry your ICM as soon as you try to start your car. One more thing that will screw things up is those oxygen sensors. It shouldn't stop the car from starting but if they are both clogged or bad your car could start and cut out as soon as the car heats up. The computer is looking for a signal and isn't getting one. I had to replace those also. I hope this helped you out.
Let me know how it goes. Later

 

I put a new ICM on today with the new ciol, at first it did not start and then a few hours later it started then shut out after about 20 minutes idleing, now it wont start again. Has anyone had any experience with a dead KS causing no spark?
Jerris

 

Code 36 is BAD news 16&36 are optispark related.I thought this thread sounded like a bad opti.Still could be the ECM or harness too.

 

The car is now starting again with only a slight miss at idle, higher RPM in nutral seems to be smooth, this leads me to believe that it is not the 4 month old Opti, but I could be wrong. It has only thrown the H36 code once before but is consistantly throwing the code 41 - EST (knock sensor ) Error, the manual says that this is " EST circuit voltage was above 4.6 volts when engine speed was under 1500 RPM." Perhaps this explains the slight miss at this RPM but smooth at higher RPM.
Has anyone had any experience with a bad knock sensor preventing their LT1 from starting?
I am having someone coming by to hook up their scanner now for further diognosis, will keep everyone posted.
I want to diognose before buying any more parts........ HELP
Jerris

 

Have you tried listening to the engine for knock?Try using some mechanics stethoscopes.Scanner is the way to go at this point it should be able to show the knock.Knock is usually either lean fuel supply or missfiring.Have you checked your fuel pressure?I do not believe a bad knock sensor will prevent the plugs from firing.All it does it make the ECM change timing to alleviate it.

At this point I think a little more history is needed to help you.Why did you replace the opti before? How many optis have you put in?What are your driving habits?Do you over rev the engine?It still looks like the opti to me your symptoms seem to indicate it.Any coolant leaks?Have you changed plugs and wires?Have you checked for corona effect(not the beer ) in a dark garage get a mist bottle fire up the car spray the wires and check for arcing.

 

Is the engine overheating?
Did you do a compression test?
Do you think the head gasket could be leaking?

 

Here is what the scanner said at capture time:
Coolant temp - 182 deg
Map sensor - 1.37
Throttle sensor0.72
Battery voltage - 13.9 V
Manifold temp 89 deg
Left oxygen sensor - 611( jumped between 286 and 611 during miss)
Right Ox sensor - 396 ( jumped between 308 and 611 during miss)
Left block learn value - 118
Right block learn value - 118
Block learn cell - 16
Left intigrator value - 122
Right intigrator value 128
CCP duty cycle - 0.0%
Idle air motor pos -70 steps (jumped between 70 and 142 during miss)
Desired idle - 687 rpm
Spark advance - 23 deg (jumped between 18 and 26 deg during miss)
Engine RPM 1075 rpm
engine run time - 217 secs
Knock retard - 0 deg
Throttle angle 0%
EGR duty cycle - 0%
Learned idle position - 53 steps
Closed loop - closed
Fan running - yes
Also showed code 41 - Electronic Spark timing open

REDCORVETTE - engine is not overheating

REDEASY SPORT - Do not hear knock, replaced Opti wires plugs and waterpump due to waterpump leak ( one Opti only), did not over rev engine before problem, will check carona effect tonight.

Scanner shows no problem with the Opti or ECM, I am starting to think that I have a bad connection in the ignition wireing somewhere, will check these tomorrow.
Thanks for your patience guys, by the way my car is also a ruby red on red and I love how your cars look.
Thanks
Jerris