Hi,
I hope someone can help. I have had my vette to a "corvette shop" twice and still have the same problem. $1000 later same issue.
I took it to the shops because while I was driving along at 70mph it started missing and then while I got off the freeway the missing and backfiring got worse. It was so back if you we looking at me driving you would have thought I couldnt drive a stick.
After a tow home, the next day the car started right up and ran normal all the way to the shop, an hour drive. The shop said they couldn't reproduce the problem so, I picked it back up. 40 min after I got it and driving in stop and go traffic, it started acting up again, missing, and getting hot, getting off freeway, hard missing, backfiring, loss of power, so I had it towed back to the shop directly. They said I had a coolant leak at thermostat. They fixed that and said they dried up around the wires and opti. Changed t-stat added coolant, then test drove it and scoped. They could not find any issues.
Once again picked it up and driving home started missing slightly like driving in wrong gear. But this clear up after shifting down into 5th. I was going up a good hill. Drove 30 min to home.
Went for a drive today, 105 deg today here in California. Drove well good no issue at all, got on the freeway, nice windy entrance so had some fun getting on (hard driving) still not a problem. No missing, great power, Go of the next exit to go back home and started missing again Slightly, but the started missing hard backfiring and seem to also to have a clutch/throwout bearing wine, had to tow it home. Once I got it home off the tow truck. Started right up and was not missing and I drove it up the driveway. Was not missing and non clutch wine. Seemed to be running normal again.

New injectors in oct 2010
New fuel filters same time
New O2 sensors same time
New plugs

No codes according to the shop. Opti according to them ok. So if those
are ok, what the heck can be the issue. Tired of getting towed home.

 

I'm betting the opti is not OK.

 

Some have said the ICM can cause this kind of performance as it gets too hot.
BUT I'm replacing my Opti next weekend to cure the same symptoms.

Good luck!

UPDATE: I replaced mmy Optispark with a Chandler unit, and all my problems went away. When I went back in the house, I also had a message on my answering machine from the Lottery bureau telling me to call them right away.
NET:
It was the Optispark... in the engine compartment... with high voltage.

 

Sure sounds like a classic Opti problem. When the moisture in your Opti gets hot and steamy it can cause backfiring and can block the optical sensor with steam. When it cools steam goes away. This should throw a code though. The moisture could also be causing spark to jump around inside the cap. It's a very short high voltage jump from the center of the rotor to the screws that hold it on.

Your Opti is non-vented and water intrusion is a very common problem on that Opti. If a water leaks on a non-vented one it's about 50/50 if it self destructs.

 

Thanks, I thought it might be the opti.

With that, which is the best? I hear bad things about rebuilds, eBay ones, etc... Is MSD good? Car is bone stock, 120,000 miles and is my daily driver.

 

I used the GM Opti, cost a little more but gave me peace of mind.

 

 

Its a 92 - please, please, please do a search here. Lots of us with LTx engines have had the same problems.
Possibilities:
wiring - connectors especially!
ICM
Coil

The opti usually throws a code before it goes.

Good luck with the parts changer mechanic. If I have to take my car to a mechanic I ALWAYS hand them my copy of the FSM. These cars are getting old and the mechanic may have never dealt with an LTx

 

I am of the L98 school, don't speak Opti but do wonder about your mechanic.

 

I have a similar problem on my 92. Please keep us posted..
My 92 just turned 40,000 and tends to get a steady miss when hot. (And it has been hot here in central Texas of late ) Sometimes mild, barely felt. Sometimes it will barf or 'buck' when the trans shifts into overdrive below 40 and I ease into the throttle. I'm still learning about the LT1, but could this be fuel related? (I guess i need to check fuel pressure).. seems to run better on a full tank. I have replaced the fuel filter.

-Frank

 

Try replacing the coil. There cheap, and easy swap. Mine has ate one factory, one accell, and I think my msd is failing now. All in 6 years.

 

Found this thread.. At least for my issue.. this is where I'll start.
http://forums.corvetteforum.com/c4-t...when-warm.html

And thinking more on when this started for me.. seemed to be around the time I was not paying attention to the fuel gauge (on reserve) and just about ran the car out of gas.

 

I didnt really want to say who was working on it, but its Corvette Specialty of California. So you would think they would be great working on my vette.

 

Turned out to be a bad fuel injector. $30 rebuilt from Amazon.

 

I had a slight miss in my 03, turned out to be the ECM.