Hey, bought a 93 corvette about 5 months ago, Everything works & ran great. One day while driving on the highway the engine just turned off. Everything else stayed on, radio, a/c everything. While coasting I put it in neutral and started it up. Ran good, got home. Than it started to happen more often until of course I wont drive it anymore.
The last few days I let it run in the driveway and it turns off when it hits 190-195. Again, everything else stays on and it will start right back up but within a minute turns off again. No check engine light or anything. Someone suggested the ignition control module so I changed that yesterday but no good. Still shuts down at 190 and starts back up.
Any help would be appreciated!

 

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I don't know from experience but a lot of people have said this could be the ICM which can cut out when hot. Or the coil. Dan

 

Heat does weird things, I had an Opti in my 93 that would shut down anywhere 185 +- replaced it along with the coil.
the best bet is study up on testing Opti

 

I started a thread yesterday for a similar problem. Engine died and wouldn't restart for me. Towed to a garage and it started for them next day after it cooled. When they let it heat up, it stalled again. It was the ICM.
Woops, just realized you tackled that already.
They also changed the coil so maybe that.

 

I now see you replaced your ICM. Many here have reported new aftermarket ICM's that are dead on arrival. When it shuts off check for spark. Dan

 

Check out your HEI coil in the dizzy cap. Mine was doing what yours is and when it finally died for good I pulled the coil and smelt it and it smelled burnt and the output was open circuit. Test then replace if bad.

Sorry I just realized you have an opti dizzy. That could be bad too.

 

Thanks for the advice! Changed the ignition control module & the coil but it still shuts down at 195. Very odd thing, if I restart it, it will turn off 2-3 times but once the temp hits 200 it stays on. I know this sounds impossible but this is what happens. I actually took a chance and drove it to an old car meet the other night and made it there and back.
Not really sure where to go from here, never heard of anything like this. There is a very good corvette repair place on long island but has a three month wait.

 

The Opti spark ignition systems in these vehicles have been known to go bad and those become intermittent too. I suggest you get yourself a factory service manual for this year and follow the troubleshooting steps before replacing anything else. Again it is very common for Opti-sparks to fail like this.

https://www.corvetteforum.com/articl...acement-guide/

 

I would start here. I had this exact problem years ago. Here's how to test it the easy way:
When you're driving down the road, in gear, it reaches 190 and the engine dies, while the engine is still spinning by being driven by the wheels, what does the tach read? If it drops to zero, you have a pick up (opti) failure. If it keeps on reading a believable value, then it's not the distributor.

 

Yes i will get the service manual. I'm sure it'll come in handy. Thank you!

 

This I will try tonight. Thank you!

 

Hey, thanks for the help. Finally got to drive the car today and the same thing happened. Once it hit 190-195 it shut off. This time I checked the RPM's and it was at zero while I was coasting. I guess this confirms the opti failure. I'm a plumber but always worked on my own cars but this looks a little tough. .At least when I find somebody to do it I feel confident that the opti is actually the problem.
Again, thank you!
Mike

 

It's pretty easy job. If you can route and sweat pipe, you can do this, too, probably.

 

Just does not seem like a opti to me. Check the codes and see if there are any in module 4. Look for error code 16 which is the low resolution pulse and if it's missing the engine can stop. But I'm betting it's not going to be there.

But it's a 93 with an ECM that is known to have strange problems. My money is on the ECM. One thing you can do is put a cold pack on top of it and see if it chances the conditions.
I wouldn't just replace it right away, but I would keep it in consideration as a possible problem.

If when the problem was happening, I would want to know if there was spark and (using a noid light) injector drive

 

I mean...he's losing tach signal. That comes from the opti.

 

I know.


If the key is on still, the trans doesn't "know" the engine shut off. Trans should still be in whatever gear, converter locked....engine, turning....same as if you released the throttle in that same gear, at that same speed, going down a hill.

 

^That's a good point; if he had to crank it, and then it started....it couldn't very well have been spinning already, but not running/"Starting".

Yeah? I've never owned a GM V8 car (or truck) that did that. Even if it did, the converter should still drive the engine...just. like in the old days, before lock up converters. Perhaps the OP can acertain if this engine is still spinning or not, by the sound/feel of the car?


Isn't that an electronically controlled trans? Is the OP's? Those didn't go into GM RWD cars until '94. The OP isn't turning his key off.

Sounds like you're right though....some more experimenting needs to be done, apparently.

 

Ok. I have followed this thread now for a couple of days to see how much wrong information will be presented. Now it's time for correct information. In fourth gear with the engine supplying power, the input to the rear planetary is the planet carrier(connected to the front ring gear). The front ring gear is being driven by the 3-4 clutch pack. With the rear sun gear locked, the rear carrier walks around it, forcing the rear ring gear to turn in an overdrive ratio.(rear ring gear is splined to the output shaft) This in turn causes the front carrier(also splined to the output shaft) to turn at the same speed. The front sun gear(connected to the sprag) spins faster than engine speed and the sprag over rides. However. That all changes when the engine is no longer the power source. The rear wheels now become the power source. The input to the rear planetary becomes the RING GEAR. This drives the rear carrier around the (still) locked rear sun gear. Since nothing mechanical has changed, the rear carrier now drives the front ring gear which is STILL connected to the 3-4 clutch pack and the input drum turns. This is only valid as long as the band is locking the rev. input drum/sunshell(4th gear). If the band releases during this action, then the over run clutches would need to be applied to maintain engine rotation. In my own case, I was travelling about 70 MPH when the engine lost power. Tach dropped to 0 for about 3-4 seconds, then lit up again. One hour later coming out of a restaurant, no start. New opti.

 

^Thank you^. I was hoping someone w/auto trans knowlege would chime in. I KNOW, rear wheels drive the engine in OD. I ain't THAT dumb.


Tach must have been "stuck" then. On 4 different trucks.

You'll have to give me a little credit that I CAN actually discern when the converter is locked...and when it's in "slush" mode. It ain't hard.


Welp....help me out here then. As you probably already know, I live at 7000' in Park city. I commute down into SLC, which is about a 3000' drop down Parley's canyon on I80. I get on at the summit, get up to speed, let off the throttle..."0%TPS". Truck is in OD, DFCO kicks in....so no injection...engine is "off" from a power production perspective. At this point, the engine is spinning ~2400 RPM or so at about 75 mph....exact same RPM at the exact same speed as if I were on the throttle on flat ground. How? Converter is unlocked, you say. Sprag shouldn't allow wheels to drive engine you say (yes I know how a sprag works). Soooo...what's turning the engine? 4 Different "all GM" trucks;
'97 1500
'05 1500
'07 Duramax
'98 1500

What's turning the engine?


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