Hey, hope i can help.... have fixed 3 high rpm misfires now....
96 lt1- loose/broken MAP sensor plug
97 lt1- plug wires
97 lt1- optispark
ANY shop your taking an lt1 to better have someone that KNOWS a scanner.

 

what was the loose map sensor showing on the scanner?

 

Here's my personal experience with this problem. I replaced the opti with a brand-new GM opti. The car started missing at high RPM two days later(at least that's when I noticed it). I ended up replacing the plugs, wires, coil, fuel filter, everything. It still missed. I then read that many of the brand new optis leave ht efactory with loose rotor screws. I dove in and pulled the cap, only to find that the screws were TIGHT.

I went ahead and loctited them anyways, and cleaned the inside of the cap and rotor with electrical contact cleaner. After reassembly I took it for a drive and it didn't miss a beat! It's been about 300 miles now, and it still pulls perfect to 6,400 RPM.

My only guess is that there was some kind of substance inside the new opti that I cleaned off when I had it apart(moisture from sitting for ten years maybe??). Nothing else was changed.

 

Or maybe one or more of the wires where lose on the opti

Thanks for your input tho!

 

Damn any news yet man?

what did the Mech. say? did they test the opti?

 

Shop is taking FOREVER!!!!!!!!!!!!!!!!!! But they are supposed to test drive it first thing friday morning and tell me if changing the valvesprings fixed it... Cross your fingers for me!!!

 

I solved my intermittent 6K+ miss (LE2 heads, cam) by replacing the MAF sensor. Never saw a code or could see it through data logging. My research revealed that a failing MAF can be tricky to diagnose.

Once I replaced the MAF sensor the miss has disappeared.

 

FIXED!!!!!!!!!!!!!!!!!!

It turned out to be valve float. Put the beehives in and BAM! High RPM miss is GONE!!!

 

congrats... wish i could figure mine out

 

Thats great news man! i know your as happy as can be!

What springs where on before that caused the valve float, did the springs just go bad or what?

 

Nope, there is no way it could have been a loose wire, because I changed the wires and it still missed. Also, when I took the cap off I never touched the wires, as I left them attached. The only thing whatsoever that was touched/changed was spraying off the inside of the opti. Anyways, I'm glad to hear your problem is fixed!

 

NOT FIXED!!!!!!!!!!!!! Car worked fine for 2 or 3 days and now it is doing it again..... 30# SVO's on the way.

 

My car has a miss above 5600 rpm. I'm kinda broke and can't afford to replace all the parts like you are doing so I just programmed it to shift at 5600. I have an auto though and that's still kind of a ****ty solution.

 

once you get it fixed i bet the ignition will be at 100%...and ready for a lil N2O

 

Whats the word on getting the injectors?