The first time the problem happened it took several attempts to start almost like it was flooded than it ran and started fine for a couple days. Now it wont start at all. It cranks to no avail and when I stop cranking
it sputters for a few seconds out the air intake almost like the the timings off. I changed the plugs, the fuel pressure checked out OK and
the spark seems to be strong. Could this be an intermittant timing issue.

 

Sounds like a dying optispark. Any codes/SES light?

 

if it was, that means you should have a DTC... indicating a bad optispark.

SES on?

Next time it won't start, floor the pedal (clear flood mode) and see if it starts.

 

No SES or Error codes are showing. Is there a way to troubleshoot optispark?

 

How many miles? My '93 had a bad opti with only 36,000 miles, it crapped out like any other distributor would due to condensation.

Before you go nuts. Check the coil wire and make sure it isn't rubbing against the water pump. I've had this happen and my symptoms were exactly as you describe.
Check all the wires to be sure they aren't touching anything they aren't supposed to be.

 

I can beat that. On my 94 the first opti went bad at 12,000 miles, and the second at 21,000 miles. I'm sure it was because of condensation. The car isn't driven much, still only has 23k on the clock.

Oh, the last go round I upgraded to the 95/96 version.


-Mike

 

46,000 well maintained miles. I am getting spark on all cylinders, I read on earlier posts about a ECM. Could I still get strong strong spark if this is bad?

 

I got bad gas about a month ago and had the same problem.

 

OPTI and Spark Test

The opti has two functions in the spark process. The first thing that happens is as the cam turns, the optical section of the optispark picks up the signals by the rotation of the shutter wheel. The pulses are sent to the PCM via the optispark electrical harness. The PCM processes the signals along with other sensor input and determines the proper time for the coil to fire. The PCM sends a signal to the Ignition Control Module (ICM) and it, in turn, causes the coil to fire. The spark from the coil travels through the coil wire back to the secondary ignition section of the optispark (cap and rotor), to be distributed to the proper cylinder.

If the opti is never sending the signal to the PCM, the PCM will never send a signal to fire the coil.

Here is some testing you can do. Refer to this diagram:



Disconnect the ICM connector. Leave coil connected.
Turn key to ON.
Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM.
Result should be 10v dc or more on both terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad.
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire).
If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM or any of the wiring in between. Visually inspect all the connections you can get to for poor contact or corrosion.

 

I've had a lot of trouble with the *&%&* opti spark, but it sounds like a problem with the ignition module.

 

Use your timing light to see if the timing is correct and constant. Measure the fuel pressure and see if it holds up after you turn the ign off. If it drops rapidly, you may have a leaky injector causing too rich a mixture to start and run. Remove the flexible coupling on the front of the MAF, you may have a clogged air filter. Pull the distributor cap and under bright light see if there is any carbon tracking inside.

 

He has an LT1.

 

http://forums.corvetteforum.com/show....php?t=1435464