I will start by thanking those who have helped me on my previous thread, "??flooded??", especially Jon from FIC.

History: Car ran great one month ago. No problems. Drove it to work one morning, went to go home at the end of the day and it would not start. Would crank, spit, occasionally diesel, but would not run. No codes, spark present when 2 plugs pulled, injectors pulsing on noid light, fuel pressure good and holding, ECM reading correct temperatures from all sensors. It was thought that the factory Multecs were a potential cause as all of them were 12.2-12.4 which is borderline. Jon sent me a set of design III bosch injectors. After my shady install job the car started(barely) but ran rough at low rpms and WOT. I got some advice from Jon and got them installed properly. Car would still not fire up nicely but would run a little better. It was actually very drivable. It would buck under WOT at low RPM (>2000) and over (4000 RPM). It ran very nice between 2000-4000 as if nothing was wrong. It would run well over 4000 so long as it was less than WOT. When giving WOT it would buck until around 2000 then run fantastic up to 4000 and then instantly start bucking again.

Now after driving it all morning I seem to be back at square one. It won't even start. Everything like it was back before I put in the new injectors. I did have it hooked up to my laptop over the past couple of days and it was running in closed loop but very lean (150-165) at times. All the sensors seem to be working. (TBP, O2, IAC, temp) Fuel quality should not be a problem as it did run very well under normal driving earlier today.

I am puzzled as to what is going on. Why did changing the injectors seem to help to get it to run at least but not perfect? Why will it not even start now? Why did it run perfectly under normal driving conditions earlier today? What could cause it to 1) not start 2) start but run poorly under WOT 3) run lean when running and 4) happen all of a sudden last month and now be intermittent?

Surely there is a clear answer to this problem that explains all the symptoms for a good diagnostician, but unfortunately I am not that person. Any takers?

 

Doc, here is an old post similar problem.. I am thinking ICM but the opti might be the problem
http://forums.corvetteforum.com/show...ghlight=icm+92

 

Jon, I read the post and I had that problem a year ago. Intermittent starting that was temperature dependant and the sys lights would flash. This was the ECM and once I figured it out and got it replaced with a working unit the car has run great for the past year. This time it does not seem to be the ECM as there are no codes, no sys lights flashing, and when it cranks it does get some gas (if it is the ECM the injectors are not pulsed at all so it is a dry crank).

I've removed the ICM but the local shop was closed by the time I got there. I missed them by 7 minutes. I will try tomorrow.

 

I'll agree that this Does sound to me like an ignition problem. Hard to explain away why it would run Lean with something like that going on, but Anyhow...

If the injectors are Firing normally (noid light) I'd be then checking the spark - preferably with a scope, so that you cold see dropout/miss, but a timing light will Work. Sometimes harder to See the problem that way, but if it won't fire enough to even Start it should be obvious.

The injectors and the ignition coil both trigger using the same pulse input from the ignition primary side - in this case the opti trigger. If Either of them is firing "normally" then that trigger is not the problem.

Of course you cannot see the puse Timing with just a visual check - and enough moisture in the optical trigger will make it very Random. Could be..

Otherwise - the ICM, or the coil. Low secondary voltage (weak or dying coil) is something a scope would show you

 

The new ICM did not seem to be the cure. I have a new coil that I am going to try now. Any tips on getting the rivets out to put the new coil on the bracket?

 

I think you have to drill the rivets out. The replacement coil should come with screws and nuts to take the place of the rivets.

Doug

 

I just finished installing the new coil. To my surprise the car fired up instantly. No hesitation. I didn't believe what I was hearing at first as I thought for sure I was going to be attempting to install a new opti in the upcoming weeks.

I've driven it and it runs amazing. It pulls hard all the way through the rpms. I hooked up my laptop and it was reading some funny numbers. Sometimes when not under load it runs the short term counts up to 180 and then back down again to the 120's. Under any sort of throttle it runs around 128. Aside from the computer readings it is running great. On a simulated dyno it pulled harder than it did prior to all this happening. The idle voltage and WOT voltage are a little off so I'm guessing it might need a little tune after the new injectors.

Overall I am very happy and hopefully this is the end of my problems.

 

,
Sounds like you found the problem