I have a 95 corvette. It's been off the road for 2 months now!!! I'm having withdrawal. Up to now the car ran strong.
The problem started aprox. 2 months ago after leaving home the car was running a little rough. It stalled while driving, but cut back in before I stopped.
I turned around at a light and it stalled dead. it did start back up "slowly" And I stumbled back home. I first suspected bad gas, but that was not the situation. The service soon light was on and DTC were 16 and 41 ( I think) its been awhile. I do have the two shop manuals and worked down the diagnostic tree and concluded it was the optispark. I have worked on other ignitions but this is my first experience with the optispark. The first one I received was physically faulty, after a few weeks I got a second opti and finally put it on
(what a fun job) Also new bosch plat. plus4 plugs and MSD 8.5 wires. I also got a water pump, it was physically defective, so another 3 days waiting for replacement. Before installing the water pump I wanted to make sure everything was O.K with the optispark install before I buried in beneath the water pump. I tried to finally fire it up after two months.

No start...great..Sooo back to the books, there were no DTC set so I assumed the optispark was doing its job. Checked for spark.
No spark at coil. I did the diagnostic tree again and it pointed to a bad Ignition coil Module. So today I replaced the whole assembly, module and new coil. Again still no spark. I did the same test that showed the ing. mod. was defective the first time....

Jump terminal B in the black coil connector to term B in the gray coil connector and jump term A in gray connector inline with a 12 volt test light to battery 12 volt source. Crank engine and the light should flash...no flash.

Still no DTC were set. This is starting to get to me. So I disconnected the optispark connector, and I assumed it should have set DTC code 16 and 41 again, because the pcm would not be receiving any reference pulses, but no codes were set. Now I'm thinking PCM (?) but this replacing parts at random is getting costly. And I am looking for any input.
Also yesterday it was setting a code for low water temp, which is O.K. because the sender is just handing there waiting for the water pump. I also had a setting for low voltage at the fuel pump. I think the system was sensing the engine not starting (possibly flooding) and was shutting down the fuel pump. I cleared the codes and today none of these codes are showing up?

The car is a 95 LT1. 66K miles Other than the flowmaster exhaust and blisten shocks, its pretty much stock.

Any ideas?
Thanks in advance

 

There was a big thread regarding JUST this problem.

Check the harness to the coil/ignition module. Make sure it's making contact.

You seem to have followed the diags properly... and I don't think the ECM is going to throw a code during startup... I need to research that to be sure... but I think the engine has to be running to get a code.

Have you checked continuity between the ECM harness and the Opti/coil/ignition module?

 

Big thead, now that's an understatement. Hey Bogus how's things? Dave I responded to your email.

Some of his symptoms sound very familiar don't they.

I found it interesting his description on the restart after the U turn where he said it started "slowly" which is of interest to me because for several weeks prior to mine going wacky sometimes in the morning when I did the first startup, instead of touching the starter and it firing to life with authority it was more like touch the starter it fired but slowly spooled up. I commented to Dave that it was to me similar to starting a turbine engine. If that is what he was referring to I find that interesting. I've never even knew a engine like this could startup like that slowly and smoothly increasing RPMs on its start. A turbine engine is like that as it passes a certain RPM and when fire is introduced turbine acceleration occurs as there is now exhaust gases to work with.

Anyway thought I'd chime in on this post as I have yet to completely solve mine as well. I have it running extremely well at normal and cruise driving configurations, but the moment it comes to a stop (auto) in gear it starts to mis fire best described like it was firing on 2/3'rds of the cylinders. Sometimes I can goose it a couple times and it behaves for a brief period of time but the roughness comes back. Pop it into neutral or park and its a perfect idle. Plus my local driving gas mileage has really dropped.

I have a new O2, wire set, TPS, full gasket set for the TB on the way in. I'm going to replace the O2, R&R the TB and swap out the taylors for a new set of AC wires. Going back to stock. I'm really suspicious of the coil wire just cause I didn't like the way it made its connection to the coil terminal. After that, as we spoke, then remove those crimps and solder the tach filter and ICM connector splices. Although I think they are good and solid as is, I just like solder to crimping.

After all this and if I don't find the answer in my new book from Probst I be drawing a blank. It would be nice if one of us identifies the faulty component here. This would sure save a lot of people a lot of anguish.

 

If the DTC won't set until the engine starts, after an optispark replacement is their a way to check if it is sending the pulses to the PCM?

 

tomorrow I will get out the DVM and check all the harnesses, tip to tip.

 

Tomorrow I will get out the DVM and check all the harnesses tip to tip. I'm running out of options....