Hi all!
Figured I'd consult the experts before I load this car on a trailer and take it to a shop ($$$).
I've got a '93 LT1 coupe with a paltry 16k miles on it (yes, it's a garage queen, and I believe that's part of the problem).
It's developed a problem as of late. Idles rough, doesn't want to rev, and pops through the pipes with a slight application of the throttle. It appears to clean out a bit at higher RPM, but doesn't make power like it used to.
Here's what I've done so far:
>Removed and meticulously cleaned the Optispark. It was full of rusty debris, and the cap and rotor showed excessive corrosion for such a low mileage car. Waterpump shows signs of weeping, so I paid close attention to properly sealing the Opti on reassembly (what a lousy design!).
>Replaced the plugs. Some of the plugs were missing the platinum tips (a symptom of an extreme lean condition?).
>Replaced fuel filter.

The only thing I haven't done yet (because I don't have the tool) is to check the fuel rail pressure. In the process of troubleshooting, I found that I can pull the plugs on both #1 & #2 injectors with no change in the way the car runs. I swapped #'s 1 & 2 with #'s 5 & 6 to determine if it's a problem with plugged injectors. No change, still #1 & 2 cylinders. Pulled injectors and flushed fuel out of the rails by turning the key on. No appreciable amount of debris/sediment. My thinking is since #1 and 2 are at the far end of the fuel rails from the fuel inlet, there's not sufficient pressure at that end to feed the front cylinders (which would contribute to the apparent lean condition). Am I on the right track? Or, could it still be a problem with the Opti?
I've already priced one out ($280 from Sam Taylor in FL) just in case. A fuel pressure regulator would be an easy out, and I'm trying to accomplish this for a reasonable amount of coin because the car's going up for sale when it's fixed.
Any help would be greatly appreciated!
(sorry so long!)

 

Even though you removed and cleaned the opti, it could very well be toast. Water and deposits have a way of working into the plastic and leaving behind a nice spot for tracking to occur. All of those symptoms point to the opti still. If you can, (I know it's a royal PIA), replace it with a new one. If the water pump is weeping, replace that too or you'll be right back in the same boat. :cheers:

 

:iagree: Sure sounds like an Opti-Crap problem If you are going to go in and replace it you may want to upgrade the whole system at this time. There is an updated vented version that is much better in design. Then there is also the High-Zoot Dynaspark aftermarket replacement as well.

Of course if you do this, the job will require several pieces to have to be replaced. The timing cover, timing chain and sprockets, the cam pin, water pump drive and also the water pump I beleive. And of course the late model vented opti unit itself. It is a considerable job and expense and especially if you go with the Dyna Spark unit.

 

Correct me if I'm wrong, but I thought I read on the DynaTech Web site that you can get a plug-and-play, direct-fit replacement Opti for 1992-93 LT1s that requires no timing cover, chain, sprocket, cam pin or water pump drive mods?

 

That is probably true of the Dynaspark unit. But at a $600 price tag one would expect all of the late model refinements built into an early unit. I was refering to a GM OEM unit, if that is used then one needs to update the corresponding parts as well.

 

If the car is not throwing any codes, then I agree that the opti should be replaced with a whole new unit. Also put some new plug wires on there when you do the swap as well if you are still running the original wires. You can also add a bead of RTV around the seals of the new unt to help it stay alive for a good long while.

 

Thanks for the responses!
I think I'm going to trailer the car to a nearby Vette specialist and have them do some diagnostics on it. They looked at the car last year (when it was exhibiting the same symptoms, but only when hot), and the car mysteriously started running fine when in their care. No codes set, and nothing done to the car.
Now that it's running lousy all the time, maybe they can pin-point the problem. I'll fix whatever's wrong, though. If it is indeed the Opti, well, I've had it out and back in once already. Once more is no big deal, I guess! :)

Just FYI...this car will be for sale once it's fixed. Pristine condition, Aqua green metallic, black interior, all options including both tops and selectable ride control. Located in Western Washington.