If his car has 75K plus miles on it why wouldn't you replace the whole opt if you were going to have to pull it anyway?

From a personal experience. I also had a high rpm miss that went on for more than a year before I found the problem. Then one night the miss got extremely bad at all rpm's abruptly. The next day it died in my garage while trying to sort out the problem. Turned out to be the opti. My rotor had come unscrewed and fell to the bottom of the cap. Replaced it and never had another miss at any rpm.

I know it's not always the problem and does get blamed easily. But you can't rule it out just because it's been a year and hasn't completely failed yet.

 

At this time, that's probably what I'll end up doing. Unfortunatly when buying the car a year and a half ago from a used dealer out of state, theres no way to tell if its the original opti or not. It just seems strange no codes were found , and that it hasn't got worse. Again the opti change will happen, however unless it dies on me I probably won't fix it.

 

Believe it or not I didn't have any codes either. There wasn't anything definitive to lead me to the opti failing until the rotor fell off! Even at that point when the car wouldn't start I wasnt' convinced until I pulled it and disassembled it. I couldn't believe what I saw.

 

Sounds exactly like an opti to me. When I bought my vette, it got lower gas mileage than I expected, had a lot of soot on the butt, and an intermittent and barely perceptible hesitation at around 4500 rpm. When driven hard I also got some popping on overrun.

Asked around on the LT1 forums and everybody said "no, if it was the opti it would be throwing codes" or "it would have died by now"

18 months later, the opti bearing started squealing. After opti replacement my mileage went up by 5 mpg, much less soot on the butt, no hesitation, no popping.

 

When in doubt, it probably is the opti. Unfortunatly, I am currently saving each nickel I earn towards an ATI D1SC for my Camaro, so the opti situation with my Formula will have to wait, unless it completely dies on me before I have the extra cash to fix it, then I'll have to break down and get it fixed.

I'll bring any updates I have later when I change it to see if it indeed was the opti. I am honestly hoping it is, just for the mere fact that if it isn't, I am really not going to have a clue what else to check. Thanks for all the inputs!

 

After reading this thread, I think you just diagnosed my car. My dyno showed the car to off by 10-20hp with a subtle shakey curve.

thanks steve

Replacing the opti sounds like the next step as I have also recently done the same changes....icm, wires, plugs. My car also has a slight stumble OTL.

 

sound like cap/rotor to me.
You did the wires/plugs so finish the tune-up with a cap/rotor.

 

My father and I just recently rebuilt the engine in my 93 z. Ran like crap at first, had the same symptoms as yours. After looking for codes and a million other things we just said screw it and bought a new opti. AWESOME change. I would definatly say swap it. You might even want to look into upgrading the opti to the newer vented style. I believe you can find plenty of info for this on the web....

 

The only other thing I would check if you are to replace a bad opti is that the reason it went out. From my Z having gone through 4 opti's in 6 months, something besides the opti was obviously the problem. It ended up being the fact I had a motor from my buddies 93 Vette, witch has the pin at the front of the Cam. That pin ended up grinding up my opti's one by one. Eventually I changed Cams and then I had no more issues. You might also want to change the waterpump while you have everything out. Unless its fairly new itself or you are confident it won't go anytime soon. Otherwise, you might be in the market for another opti when the water pump goes.