'93 Convertible m6 Vette w/ 153k miles

So I was out for a drive a few days ago, when my Vette just shut down while going down the road, like I turned off the ignition. I tried and was able to get it to restart a few times, but when I'd start trying to drive the car again, it would just shut down again about the time I would get it in 3rd gear. While trying to get it started while it was still rolling, a couple times it backfired and blew a puff of black smoke. It eventually stopped restarting at all. When I was trying to start it while this was happening, my tach would show the engine turning over. But now that the car will not start, when I try to start it, I get no indication from the tach that the engine is turning over. Car is not giving any trouble codes. Does this sound like my optispark died?

edit: added info about what the tach was doing during this and what is doing now when I try to start the car.

 

 

everyone agree?

 

https://www.ebay.com/itm/LT-1-Optisp...oAAOSwX9FZIPv2
Your next question is which one to buy. I highly recommend this seller. Dan

 

Do I buy a remanfactured opti with a new Mitsubishi sensor for +$400, or do I buy a used OEM opti from a wrecked low mileage C4 for $150 plus shipping?

 

Your call. Do you feel lucky? Well, do ya 1st VetteFinally? Dan PS: Hope you are old enough to remember Dirty Harry.

 

I am (47 this July)

 

I have one of his opti's for my 96. It was put together very professionally. Sealed very well. It was tested and works perfect. Big giant huge advantage for you is he puts a ventilation system on yours that was not stock and will not be on a used unit. The other way to go about this is I can give you his email in a PM and if you have the time he can rebuild yours for $280.00 (I think). Maybe take a week. If this is not your daily driver this is the way I would go. I got a rebuilt unit from him and after it was in and working perfect I sent him my original 1996 opti and had him rebuild it for a spare. Sure hope I never need it. To repeat myself, if you have a week to spare just let him rebuild yours and add a ventilation kit. PM me for his email. His work is beautiful. I am not connected with him at all. Look at the pictures in his ebay ad and look at his workbench and you can see he is a perfectionist. Dan

 

https://www.ebay.com/itm/Optispark-r...0AAOSwVm5ZARQg
Ad does not say he adds a ventilation system. You would have to ask him about this. You really want this. Dan

 

 

Yeah, I'm not trying to go the cheap remanufactured route. What I was considering was either getting one like Whaleman posted a link to, or getting a used original opti off a wrecked low mileage C4 (40k miles or less).

 

Do you have a week for Brad to rebuild yours? I would never choose the used one off a wreck. Dan

 

No! While some symptoms sound like an Opti, others do not:
"When I was trying to start it while this was happening, my tach would show the engine turning over."
Did you even check to see if you had spark? I'd certainly do that, but for buying and R&R'ing a distributor.

 

Here is one of the pictures Brad sent me of my opti when he was rebuilding it, looks like some oil seepage. IF IT IS THE OPTI (listen to Tom400CFI), I would definitely send the unit to him, he can turn it around in a week or less

 

He does a great job and that is why I recommended him. I am glad you agree. Hard to believe with all that oil the sender was still good but they are tough old birds. Dan

 

I bought an AIP unit and swapped in my Mitsubishi sensor, just for the heck of it.
If I could locate the proper two shoulder bearing, I'd do the dang thing myself. I tried the one shoulder bearing that was recommended and it had a wiggle, regardless of which direction I installed it. I'd like to know which bearing the rebuilders are using.

 

The opti, as with other distributors, is a two-segment device. There's a low-voltage segment that senses camshaft position, velocity and acceleration, and feeds that info to the ECM by way of two pulse trains (low-resolution for position, high-resolution for velocity and acceleration). If there's a fault in this part of the unit, there should be at least one DTC stored in memory. The ECM can run the engine, albeit not optimally, without the high-resolution signals, but it will not fire the coil if a low-resolution fault is detected.

And, there's the high-voltage segment, which distributes spark from the coil to the appropriate spark plug via the rotor and cap. A fault on this side of the unit will not directly trigger a DTC.

In most cases, an abrupt shut-down without any misfiring/crossfiring will not be the result of a failure on the high-voltage side. Most high-voltage side failures will lead to misfire/crossfire from the development of moisture and/or carbon tracking within the cap. Occasionally, something more spectacular goes wrong, such as a rotor that breaks apart, etc.

A fault on the sensor side will often lead to an abrupt shutdown without a lot of crossfiring as commonly occurs with a high-voltage side fault, but it should set a DTC.

Check for stored DTCs, verify the presence/absence of spark, and proceed from there before you start shopping for replacement parts. The opti is often presumed, erroneously, to be the source of trouble, when in fact it isn't. Troubleshoot the problem methodically, then take remedial steps as necessary.

Live well,

SJW

 

isn't no reaction of the tach while the engine is turning over a clear indication of a dead opti? That's what it is doing now.

I haven't spent any money on this, yet. And I haven't really had a chance to do much trouble shooting yet. It is getting fuel to the rail, and does not even try to fire, so I am thinking this is a lack of fire issue (keyword "thinking" as I have not properly trouble shot the problem yet). So I'm just getting my thoughts straight as to what I believe is wrong with the car and what's going to be involved with fixing it, provided I am correct. I should know a lot more later today.

 

Yeah; no tach signal = pretty strong evidence that the opti isn't working. It's proof that the ECM isn't getting a signal, so it's either the opti or the harness for it.

You said earlier that it wouldn't run but DID have a tach signal...so that threw a flag for me, that it may not be the opti. Some times the tach doesn't move much at cranking speed (starter) so it can be a little hard to determine if you have a tach signal using that method. I use my scan tool....but not everyone has one.


Yep so do a quick check for spark at one of the spark plugs...or at the main coil wire.

 

Well it was just too wet yesterday to mess with the car.

@Tom400CFI

Actually, what I said was as this started to happen, the car would stall out while going down the road. At first, I could get it to restart (this is when I was still getting a reaction from the tach when I would turn the car over trying to start it). After the car restarted, I would try to drive the car, but couldn't make it far enough down the road to get the car past third gear without it stalling again. A couple times during this, while trying to restart the car, the car backfired though the exhaust and blew a black cloud of smoke (very similar to the smoke my last car blew when it had bad O2 sensors). The car eventually stopped restarting, and this is when the tach stopped reacting to me trying to start the car.

So Tom, does this sound like a bad opti to you, now that I explained what happen a little better? About what you were saying about tach not moving much because of a slow turing starter. My current starter is pretty strong, and before this, when I would turn the car over to start it, my tach would read between 300-400 rpms, so that wouldn't be an issue with this particular car. I do value your opinion Tom as I feel you're one of the more knowledgeable people on these forums.